- DI String Match
- N-ary Tree Postorder Traversal
- N-ary Tree Preorder Traversal
- Search in a Binary Search Tree
- Maximum Units on a Truck
- Minimum Cost to Move Chips to The Same Position
- Lucky Numbers in a Matrix
- Delete Columns to Make Sorted
- Maximum Depth of N-ary Tree
- Middle of the Linked List
- Maximum Depth of Binary Tree
- Delete Node in a Linked List
- Remove Palindromic Subsequences
- Projection Area of 3D Shapes
- Invert Binary Tree
- Remove Palindromic Subsequences
- Available Captures for Rook
- Find the Middle Index in Array
- Minimum Changes To Make Alternating Binary String
- Rank Transform of an Array
- Find All Numbers Disappeared in an Array
1920. Build Array from Permutation
Source: https://leetcode.com/problems/build-array-from-permutation/
Difficulty: Easy
func buildArray(_ nums: [Int]) -> [Int] {
var stack = [Int]()
var result = [Int]()
for i in 0..<nums.count {
stack.append(nums[i])
}
for j in stack {
result.append(nums[j])
}
return result
}1929. Concatenation of Array
Source: https://leetcode.com/problems/concatenation-of-array/
Difficulty: Easy
func getConcatenation(_ nums: [Int]) -> [Int] {
var stack = [Int]()
for i in 0..<nums.count {
stack.append(nums[i])
}
for i in 0..<nums.count {
stack.append(nums[i])
}
return stack
}1480. Running Sum of 1d Array
Source: https://leetcode.com/problems/running-sum-of-1d-array/
Difficulty: Easy
func runningSum(_ nums: [Int]) -> [Int] {
var stack = [Int]()
func sum(index: Int) -> Int {
var temp = 0
for i in 0...index {
temp += nums[i]
}
return temp
}
for i in 0..<nums.count {
stack.append(sum(index: i))
}
return stack
}1108. Defanging an IP Address
Source: https://leetcode.com/problems/defanging-an-ip-address/
Difficulty: Easy
func defangIPaddr(_ address: String) -> String {
var charArray = [String]()
for i in address {
charArray.append(String(i))
}
for i in 0..<charArray.count {
if charArray[i] == "." {
charArray[i] = String("[.]")
}
}
var result = ""
for i in 0..<charArray.count {
result += String(charArray[i])
}
return result
}1672. Richest Customer Wealth
Source: https://leetcode.com/problems/richest-customer-wealth/
Difficulty: Easy
func maximumWealth(_ accounts: [[Int]]) -> Int {
var stack = [Int]()
for i in accounts {
let wealth = i.reduce(0) { $0 + $1 }
stack.append(wealth)
}
return stack.max()!
}1470. Shuffle the Array
Source: https://leetcode.com/problems/shuffle-the-array/
Difficulty: Easy
func shuffle(_ nums: [Int], _ n: Int) -> [Int] {
let separator = nums.count / 2 - 1
var firstHalf = [Int]()
var lastHalf = [Int]()
var result = [Int]()
for i in 0...separator {
firstHalf.append(nums[i])
}
for i in (separator + 1)..<nums.count {
lastHalf.append(nums[i])
}
for i in 0..<first.count {
result.append(firstHalf[i])
result.append(lastHalf[i])
}
return result
}1431. Kids With the Greatest Number of Candies
Source: https://leetcode.com/problems/kids-with-the-greatest-number-of-candies/
Difficulty: Easy
func kidsWithCandies(_ candies: [Int], _ extraCandies: Int) -> [Bool] {
var result = [Bool]()
var can = candies
for i in 0..<can.count {
can[i] += extraCandies
if can[i] == can.max()! {
result.append(true)
} else {
result.append(false)
}
can[i] -= extraCandies
}
return result
}1512. Number of Good Pairs
Source: https://leetcode.com/problems/number-of-good-pairs/
Difficulty: Easy
func numIdenticalPairs(_ nums: [Int]) -> Int {
var count = 0
for i in 0..<nums.count {
for j in 0..<nums.count {
if i < j && nums[i] == nums[j] {
count += 1
}
}
}
return count
}771. Jewels and Stones
Source: https://leetcode.com/problems/jewels-and-stones/
Difficulty: Easy
func numJewelsInStones(_ jewels: String, _ stones: String) -> Int {
var count = 0
for i in jewels {
count += stones.filter { $0 == i }.count
}
return count
}1365. How Many Numbers Are Smaller Than the Current Number
Source: https://leetcode.com/problems/how-many-numbers-are-smaller-than-the-current-number/
Difficulty: Easy
func smallerNumbersThanCurrent(_ nums: [Int]) -> [Int] {
var result = [Int]()
for i in nums {
let smallerCount = nums.filter { $0 < i }.count
result.append(smallerCount)
}
return result
}1528. Shuffle String
Source: https://leetcode.com/problems/shuffle-string/
Difficulty: Easy
func restoreString(_ s: String, _ indices: [Int]) -> String {
var temp = [(String, Int)]()
for i in s {
temp.append((String(i), 0))
}
for i in 0..<indices.count {
temp[i].1 = indices[i]
}
var result = ""
for i in 0..<temp.count {
let a = temp.filter { $0.1 == i }[0].0
result.append(a)
}
return result
}1281. Subtract the Product and Sum of Digits of an Integer
Source: https://leetcode.com/problems/subtract-the-product-and-sum-of-digits-of-an-integer/
Difficulty: Easy
func subtractProductAndSum(_ n: Int) -> Int {
var str = String(n)
var temp = [String]()
for i in str {
temp.append(String(i))
}
var sum = 0
var s = 1
for i in temp {
sum = sum + Int(i)!
}
for i in temp {
s = s * Int(i)!
}
return s - sum
}1313. Decompress Run-Length Encoded List
Source: https://leetcode.com/problems/decompress-run-length-encoded-list/
Difficulty: Easy
func decompressRLElist(_ nums: [Int]) -> [Int] {
var result = [Int]()
var num = nums
while !num.isEmpty {
for _ in 1...num[0] {
result.append(num[1])
}
num.removeFirst()
num.removeFirst()
}
return result
}1342. Number of Steps to Reduce a Number to Zero
Source: https://leetcode.com/problems/number-of-steps-to-reduce-a-number-to-zero/
Difficulty: Easy
func numberOfSteps(_ num: Int) -> Int {
var a = num
var count = 0
while a != 0 {
if a % 2 == 0 {
a = a / 2
count += 1
} else {
a = a - 1
count += 1
}
}
return count
}1389. Create Target Array in the Given Order
Source: https://leetcode.com/problems/create-target-array-in-the-given-order/
Difficulty: Easy
func createTargetArray(_ nums: [Int], _ index: [Int]) -> [Int] {
var target = [Int]()
for i in 0..<nums.count {
target.insert(nums[i], at: index[i])
}
return target
}1773. Count Items Matching a Rule
Source: https://leetcode.com/problems/count-items-matching-a-rule/
Difficulty: Easy
func countMatches(_ items: [[String]], _ ruleKey: String, _ ruleValue: String) -> Int {
var index = 0
var count = 0
if ruleKey == "type" {
index = 0
} else if ruleKey == "color" {
index = 1
} else if ruleKey == "name" {
index = 2
}
for i in items {
if i[index] == ruleValue {
count += 1
} else {
}
}
return count
}1221. Split a String in Balanced Strings
Source: https://leetcode.com/problems/split-a-string-in-balanced-strings/
Difficulty: Easy
func balancedStringSplit(_ s: String) -> Int {
var count = 0
var temp = 0
for i in s {
if i == "L" {
count += 1
if count == 0 {
temp += 1
} else {
}
} else if i == "R" {
count -= 1
if count == 0 {
temp += 1
} else {
}
} else {
}
}
return temp
}1791. Find Center of Star Graph
Source: https://leetcode.com/problems/find-center-of-star-graph/
Difficulty: Easy
func findCenter(_ edges: [[Int]]) -> Int {
let first = edges[0].sorted()
let second = edges[1].sorted()
if first[0] == second[0] {
return first[0]
} else {
return first[1]
}
}1859. Sorting the Sentence
Source: https://leetcode.com/problems/sorting-the-sentence/
Difficulty: Easy
func sortSentence(_ s: String) -> String {
var stringArray = s.components(separatedBy: " ")
var index = [(Int, String)]()
for i in stringArray {
let range = i.index(i.startIndex, offsetBy: 0)...i.index(i.endIndex, offsetBy: -2)
index.append((Int(i.suffix(1))!, String(i[range])))
}
var result = ""
for i in 1...index.count {
let filter = index.filter { $0.0 == i }[0].1
result.append(filter)
if i != index.count {
result.append(" ")
}
}
return result
}1688. Count of Matches in Tournament
Source: https://leetcode.com/problems/count-of-matches-in-tournament/
Difficulty: Easy
func numberOfMatches(_ n: Int) -> Int {
var teams = n
var count = 0
func cal(input: Int) {
if teams % 2 == 0 {
count += teams / 2
teams = teams / 2
} else if teams % 2 == 1 {
count += (teams - 1) / 2
teams = teams / 2 + 1
}
}
while teams != 1 {
cal(input: teams)
}
return count
}1662. Check If Two String Arrays are Equivalent
Source: https://leetcode.com/problems/check-if-two-string-arrays-are-equivalent/
Difficulty: Easy
func arrayStringsAreEqual(_ word1: [String], _ word2: [String]) -> Bool {
var one = ""
var two = ""
for i in word1 {
one += i
}
for i in word2 {
two += i
}
return one == two
}1832. Check if the Sentence Is Pangram
Source: https://leetcode.com/problems/check-if-the-sentence-is-pangram/
Difficulty: Easy
func checkIfPangram(_ sentence: String) -> Bool {
var set = Set<Character>()
for i in sentence {
set.insert(i)
}
if set.count < 26 {
return false
} else {
return true
}
}1684. Count the Number of Consistent Strings
Source: https://leetcode.com/problems/count-the-number-of-consistent-strings/
Difficulty: Easy
func countConsistentStrings(_ allowed: String, _ words: [String]) -> Int {
var allowedArray = Array(allowed)
var allowedSet = Set(allowedArray)
var result = 0
for i in words {
let wordsCount = i.count
var count = 0
for j in i {
for k in allowedSet {
if j == k {
count += 1
}
}
}
if count == wordsCount {
result += 1
}
}
return result
}1913. Maximum Product Difference Between Two Pairs
Source: https://leetcode.com/problems/maximum-product-difference-between-two-pairs/
Difficulty: Easy
func maxProductDifference(_ nums: [Int]) -> Int {
let ordered = nums.sorted(by: < )
let min = ordered[0] * ordered[1]
let max = ordered[ordered.count-2] * ordered[ordered.count-1]
return max - min
}709. To Lower Case
Source: https://leetcode.com/problems/to-lower-case/
Difficulty: Easy
func toLowerCase(_ s: String) -> String {
return s.lowercased()
}1979. Find Greatest Common Divisor of Array
Source: https://leetcode.com/problems/find-greatest-common-divisor-of-array/
Difficulty: Easy
func findGCD(_ nums: [Int]) -> Int {
let maxValue = nums.max()!
let minValue = nums.min()!
var value = Int()
var maxGCD = [Int]()
var minGCD = [Int]()
for i in 1...maxValue {
if maxValue % i == 0 {
maxGCD.append(i)
}
}
for i in 1...minValue {
if minValue % i == 0 {
minGCD.append(i)
}
}
for i in maxGCD {
for j in minGCD {
if i == j {
value = max(i, value)
}
}
}
return value
}1816. Truncate Sentence
Source: https://leetcode.com/problems/truncate-sentence/
Difficulty: Easy
func truncateSentence(_ s: String, _ k: Int) -> String {
let str = s.components(separatedBy: " ")
var result = ""
for i in 0..<k {
result.append(String(str[i]))
result.append(" ")
}
result.removeLast()
return result
}1844. Replace All Digits with Characters
Source: https://leetcode.com/problems/replace-all-digits-with-characters/
Difficulty: Easy
func replaceDigits(_ s: String) -> String {
let dict: [(Int, Character)] = [(0, "a"), (1, "b"), (2, "c"), (3, "d"), (4, "e"),
(5, "f"), (6, "g"), (7, "h"), (8, "i"), (9, "j"),
(10, "k"), (11, "l"), (12, "m"), (13, "n"), (14, "o"),
(15, "p"), (16, "q"), (17, "r"), (18, "s"), (19, "t"),
(20, "u"), (21, "v"), (22, "w"), (23, "x"), (24, "y"),
(25, "z")]
var temp = [Character]()
for i in s {
if i.isLetter {
temp.append(i)
} else {
let leftInt = dict.filter { $0.1 == temp.last }[0].0
let index = leftInt + Int(String(i))!
let filter = dict.filter { $0.0 == index }[0].1
temp.append(filter)
}
}
return String(temp)
}2000. Reverse Prefix of Word
Source: https://leetcode.com/problems/reverse-prefix-of-word/
Difficulty: Easy
func reversePrefix(_ word: String, _ ch: Character) -> String {
let charArr = Array(word)
if !charArr.contains(ch) {
return word
} else {
let firstInd = charArr.firstIndex(of: ch)!
let left = charArr[0...firstInd].reversed()
let right = charArr[(firstInd + 1)...]
return String(left) + String(right)
}
}1572. Matrix Diagonal Sum
Source: https://leetcode.com/problems/matrix-diagonal-sum/
Difficulty: Easy
func diagonalSum(_ mat: [[Int]]) -> Int {
var value = 0
for i in 0..<mat.count {
value += mat[i][i]
}
for i in 0..<mat.count {
value += mat[mat.count - 1 - i][i]
}
if mat.count % 2 == 1 {
value -= mat[mat.count / 2][mat.count / 2]
return value
} else {
return value
}
}1295. Find Numbers with Even Number of Digits
Source: https://leetcode.com/problems/find-numbers-with-even-number-of-digits/
Difficulty: Easy
func findNumbers(_ nums: [Int]) -> Int {
let strNums = nums.map { String($0) }
var count = 0
for i in strNums {
if i.count % 2 == 0 {
count += 1
} else {
count += 0
}
}
return count
}1464. Maximum Product of Two Elements in an Array
Source: https://leetcode.com/problems/maximum-product-of-two-elements-in-an-array/
Difficulty: Easy
func maxProduct(_ nums: [Int]) -> Int {
let ordered = nums.sorted(by: < )
let max = ordered[ordered.count - 1]
let maxLagged = ordered[ordered.count - 2]
return (max - 1) * (maxLagged - 1)
}1967. Number of Strings That Appear as Substrings in Word
Source: https://leetcode.com/problems/number-of-strings-that-appear-as-substrings-in-word/
Difficulty: Easy
func numOfStrings(_ patterns: [String], _ word: String) -> Int {
var count = 0
for i in patterns {
if word.contains(i) {
count += 1
}
}
return count
}1436. Destination City
Source: https://leetcode.com/problems/destination-city/
Difficulty: Easy
func destCity(_ paths: [[String]]) -> String {
var dict = [String:String]()
var current = paths[0][0]
for i in paths {
dict[i[0]] = i[1]
}
while dict.keys.contains(current) {
current = dict[current]!
}
return current
}1941. Check if All Characters Have Equal Number of Occurrences
Source: https://leetcode.com/problems/check-if-all-characters-have-equal-number-of-occurrences/
Difficulty: Easy
func areOccurrencesEqual(_ s: String) -> Bool {
var dict = [String:Int]()
for i in s {
dict[String(i), default: 0] += 1
}
var count = [Int]()
for (key, value) in dict {
count.append(value)
}
if count.filter { $0 == count[0] }.count == count.count {
return true
} else {
return false
}
}1450. Number of Students Doing Homework at a Given Time
Source: https://leetcode.com/problems/number-of-students-doing-homework-at-a-given-time/
Difficulty: Easy
func busyStudent(_ startTime: [Int], _ endTime: [Int], _ queryTime: Int) -> Int {
var count = 0
for i in 0..<startTime.count {
if startTime[i] <= queryTime && endTime[i] >= queryTime {
count += 1
}
}
return count
}728. Self Dividing Numbers
Source: https://leetcode.com/problems/self-dividing-numbers/
Difficulty: Easy
func isSelfDivi(input: Int) -> Bool {
let temp = Array(String(input))
var stack = [Character]()
var ind = 0
if temp.contains("0") {
return false
}
while ind < temp.count {
if input % Int(String(temp[ind]))! == 0 {
stack.append(temp[ind])
}
ind += 1
}
return stack.count == temp.count
}
func selfDividingNumbers(_ left: Int, _ right: Int) -> [Int] {
var result = [Int]()
for i in left...right {
if isSelfDivi(input: i) {
result.append(i)
}
}
return result
}1837. Sum of Digits in Base K
Source: https://leetcode.com/problems/sum-of-digits-in-base-k/
Difficulty: Easy
func sumBase(_ n: Int, _ k: Int) -> Int {
var temp = n
var str = ""
while temp != 0 {
str += String(temp % k)
temp = temp / k
}
var result = 0
for i in str {
result += Int(String(i))!
}
return result
}1351. Count Negative Numbers in a Sorted Matrix
Source: https://leetcode.com/problems/count-negative-numbers-in-a-sorted-matrix/
Difficulty: Easy
func countNegatives(_ grid: [[Int]]) -> Int {
var count = 0
for i in 0..<grid.count {
for j in 0..<grid[0].count {
if grid[i][j] < 0 {
count += 1
}
}
}
return count
}961. N-Repeated Element in Size 2N Array
Source: https://leetcode.com/problems/n-repeated-element-in-size-2n-array/
Difficulty: Easy
func repeatedNTimes(_ nums: [Int]) -> Int {
var count = 0
var sorted = nums.sorted()
var left = sorted[count]
var right = sorted[count+1]
while left != right {
count += 1
left = sorted[count]
right = sorted[count+1]
}
return left
}905. Sort Array By Parity
Source: https://leetcode.com/problems/sort-array-by-parity/
Difficulty: Easy
func sortArrayByParity(_ nums: [Int]) -> [Int] {
let even = nums.filter { $0 % 2 == 0 }
let odd = nums.filter { $0 % 2 == 1 }
var result = [Int]()
for i in even {
result.append(i)
}
for i in odd {
result.append(i)
}
return result
}1748. Sum of Unique Elements
Source: https://leetcode.com/problems/sum-of-unique-elements/
Difficulty: Easy
func sumOfUnique(_ nums: [Int]) -> Int {
var dict = [Int:Int]()
for i in nums {
dict[i, default: 0] += 1
}
var result = 0
for (key, value) in dict {
if value == 1 {
result += key
}
}
return result
}1475. Final Prices With a Special Discount in a Shop
Source: https://leetcode.com/problems/final-prices-with-a-special-discount-in-a-shop/
Difficulty: Easy
func finalPrices(_ prices: [Int]) -> [Int] {
var result = [Int]()
for i in 0..<prices.count {
let filter = prices[(i + 1)...].filter { $0 <= prices[i] }
if filter.isEmpty {
result.append(prices[i])
} else {
result.append(prices[i] - filter.first!)
}
}
return result
}657. Robot Return to Origin
Source: https://leetcode.com/problems/robot-return-to-origin/
Difficulty: Easy
func judgeCircle(_ moves: String) -> Bool {
let uCount = moves.filter { $0 == "U" }.count
let dCount = moves.filter { $0 == "D" }.count * -1
let rCount = moves.filter { $0 == "R" }.count
let lCount = moves.filter { $0 == "L" }.count * -1
if uCount + dCount == 0 && rCount + lCount == 0 {
return true
} else {
return false
}
}561. Array Partition I
Source: https://leetcode.com/problems/array-partition-i/
Difficulty: Easy
func arrayPairSum(_ nums: [Int]) -> Int {
let sorted = nums.sorted(by: >)
var i = 1
var result = 0
while i < sorted.count {
result += sorted[i]
i += 2
}
return result
}557. Reverse Words in a String III
Source: https://leetcode.com/problems/reverse-words-in-a-string-iii/
Difficulty: Easy
func reverseWords(_ s: String) -> String {
let strArr = s.components(separatedBy: " ").map { $0.reversed() }
var result = ""
for i in strArr {
result += i
result
+= " "
}
result.removeLast()
return result
}1051. Height Checker
Source: https://leetcode.com/problems/height-checker/
Difficulty: Easy
func heightChecker(_ heights: [Int]) -> Int {
var sorted = heights.sorted(by: <)
var count = 0
for i in 0..<sorted.count {
if heights[i] != sorted[i] {
count += 1
} else {
}
}
return count
}1742. Maximum Number of Balls in a Box
Source: https://leetcode.com/problems/maximum-number-of-balls-in-a-box/
Difficulty: Easy
func digits(value: Int) -> Int {
let charInt = Array(String(value))
return charInt.map { Int(String($0))! }.reduce(0) { $0 + $1 }
}
func countBalls(_ lowLimit: Int, _ highLimit: Int) -> Int {
var dict = [Int:Int]()
var result = 0
for i in lowLimit...highLimit {
dict[digits(value: i), default: 0] += 1
}
for (key, value) in dict {
result = max(result, value)
}
return result
}1935. Maximum Number of Words You Can Type
Source: https://leetcode.com/problems/maximum-number-of-words-you-can-type/
Difficulty: Easy
func canBeTypedWords(_ text: String, _ brokenLetters: String) -> Int {
let brkLetters = Array(brokenLetters)
var wordArr = text.components(separatedBy: " ")
for i in brkLetters {
for j in 0..<wordArr.count {
if wordArr[j].contains(i) {
wordArr[j] = ""
}
}
}
return wordArr.filter { $0 != "" }.count
}1207. Unique Number of Occurrences
Source: https://leetcode.com/problems/unique-number-of-occurrences/
Difficulty: Easy
func uniqueOccurrences(_ arr: [Int]) -> Bool {
var dict = [Int:Int]()
var set = Set<Int>()
var array = [Int]()
for i in arr {
dict[i, default: 0] += 1
}
for (key, value) in dict {
set.insert(value)
array.append(value)
}
return set.count == array.count
}1880. Check if Word Equals Summation of Two Words
Source: https://leetcode.com/problems/check-if-word-equals-summation-of-two-words/
Difficulty: Easy
func isSumEqual(_ firstWord: String, _ secondWord: String, _ targetWord: String) -> Bool {
let dict: [Character:String] = ["a":"0", "b":"1", "c":"2", "d":"3", "e": "4",
"f":"5", "g":"6", "h":"7", "i":"8", "j":"9",
"k":"10", "l":"11", "m":"12", "n":"13", "o":"14",
"p":"15", "q":"16", "r":"17", "s":"18", "t":"19",
"u":"20", "v":"21", "w":"22", "x":"23", "y":"24",
"z":"25"]
var first = ""
var second = ""
var target = ""
for i in firstWord {
first += dict[i]!
}
for i in secondWord {
second += dict[i]!
}
for i in targetWord {
target += dict[i]!
}
return Int(first)! + Int(second)! == Int(target)
}344. Reverse String
Source: https://leetcode.com/problems/reverse-string/
Difficulty: Easy
func reverseString(_ s: inout [Character]) {
var left = 0
var right = s.count - 1
while left < right {
s.swapAt(left, right)
left += 1
right -= 1
}
}1337. The K Weakest Rows in a Matrix
Source: https://leetcode.com/problems/the-k-weakest-rows-in-a-matrix/
Difficulty: Easy
func kWeakestRows(_ mat: [[Int]], _ k: Int) -> [Int] {
var dict = [(Int, Int)]()
var result = [Int]()
for i in 0..<mat.count {
dict.append((i, mat[i].reduce(0) { $0 + $1 }))
}
dict.sort { $0.1 < $1.1 || $0.0 < $1.0 }
for i in 0..<k {
result.append(dict[i].0)
}
return result
}1403. Minimum Subsequence in Non-Increasing Order
Source: https://leetcode.com/problems/minimum-subsequence-in-non-increasing-order/
Difficulty: Easy
func minSubsequence(_ nums: [Int]) -> [Int] {
var ordered = nums.sorted(by: > )
var result = [Int]()
if nums.count == 1 {
result = nums
} else if nums.isEmpty {
result = []
}
for i in 0..<nums.count - 1 {
let left = ordered[0...i].reduce(0) { $0 + $1 }
let right = ordered[(i + 1)...(nums.count - 1)].reduce(0) { $0 + $1 }
if left > right {
for i in ordered[0...i] {
result.append(i)
}
break
}
}
if Set(nums).count == 1 {
return nums
}
return result
}338. Counting Bits
Source: https://leetcode.com/problems/counting-bits/
Difficulty: Easy
func binaryBits(_ input: Int) -> Int {
var temp = input
var count = 0
while temp != 0 {
if temp % 2 == 1 {
count += 1
}
temp = temp / 2
}
return count
}
func countBits(_ n: Int) -> [Int] {
var result = [Int]()
for i in 0...n {
result.append(binaryBits(i))
}
return result
}977. Squares of a Sorted Array
Source: https://leetcode.com/problems/squares-of-a-sorted-array/
Difficulty: Easy
func sortedSquares(_ nums: [Int]) -> [Int] {
var result = [Int]()
for i in nums {
result.append(i * i)
}
return result.sorted(by: < )
}852. Peak Index in a Mountain Array
Source: https://leetcode.com/problems/peak-index-in-a-mountain-array/
Difficulty: Easy
func peakIndexInMountainArray(_ arr: [Int]) -> Int {
var left = 0
var right = 1
while right < arr.count {
if arr[left] <= arr[right] {
left += 1
right += 1
} else {
break
}
}
return right - 1
}1047. Remove All Adjacent Duplicates In String
Source: https://leetcode.com/problems/remove-all-adjacent-duplicates-in-string/
Difficulty: Easy
func removeDuplicates(_ s: String) -> String {
var stack = [Character]()
for i in s {
if stack.isEmpty || i != stack.last {
stack.append(i)
} else if !stack.isEmpty || i == stack.last {
stack.removeLast()
}
}
return String(stack)
}1356. Sort Integers by The Number of 1 Bits
Source: https://leetcode.com/problems/sort-integers-by-the-number-of-1-bits/
Difficulty: Easy
func sortByBits(_ arr: [Int]) -> [Int] {
var dict = [(Int, Int)]()
var result = [Int]()
for i in arr {
var temp = i
var count = 0
while temp != 0 {
if temp % 2 == 1 {
count += 1
}
temp = temp / 2
}
dict.append((i, count))
}
dict.sort { $0.0 < $1.0 }
dict.sort { $0.1 < $1.1 }
for i in dict {
result.append(i.0)
}
return result
}922. Sort Array By Parity II
Source: https://leetcode.com/problems/sort-array-by-parity-ii/
Difficulty: Easy
func sortArrayByParityII(_ nums: [Int]) -> [Int] {
var result = Array(repeating: 0, count: nums.count)
var odd = [Int]()
var even = [Int]()
for i in nums {
if i % 2 == 0 {
even.append(i)
} else if i % 2 == 1 {
odd.append(i)
}
}
for i in 0..<odd.count {
result[i * 2 + 1] = odd[i]
}
for i in 0..<even.count {
result[i * 2] = even[i]
}
return result
}1441. Build an Array With Stack Operations
Source: https://leetcode.com/problems/build-an-array-with-stack-operations/
Difficulty: Easy
func buildArray(_ target: [Int], _ n: Int) -> [String] {
var index = 0
var temp = 1
var result = [String]()
while index < target.count {
if target[index] == temp {
result.append("Push")
index += 1
} else {
result.append("Push")
result.append("Pop")
}
temp += 1
}
return result
}821. Shortest Distance to a Character
Source: https://leetcode.com/problems/shortest-distance-to-a-character/
Difficulty: Easy
func shortestToChar(_ s: String, _ c: Character) -> [Int] {
var result = Array(repeating:0, count: s.count)
for i in 0..<s.count {
result[i] = i
}
var cIndice = [Int]()
var index = 0
for i in s {
if i == c {
cIndice.append(index)
}
index += 1
}
for i in 0..<result.count {
var temp = s.count
for j in cIndice {
temp = min(temp, abs(i - j))
}
result[i] = temp
}
return result
}1502. Can Make Arithmetic Progression From Sequence
Source: https://leetcode.com/problems/can-make-arithmetic-progression-from-sequence/
Difficulty: Easy
func canMakeArithmeticProgression(_ arr: [Int]) -> Bool {
let sorted = arr.sorted(by: < )
let val = sorted[1] - sorted[0]
var left = 0
var right = 1
while right < sorted.count {
if sorted[left] + val == sorted[right] {
left += 1
right += 1
} else {
return false
}
}
return right == sorted.count
}1876. Substrings of Size Three with Distinct Characters
Source: https://leetcode.com/problems/substrings-of-size-three-with-distinct-characters/
Difficulty: Easy
func countGoodSubstrings(_ s: String) -> Int {
let char = Array(s)
var startInd = 0
var rangeInd = 2
var str = [String]()
var count = 0
while rangeInd < s.count {
let temp = char[startInd...rangeInd]
str.append(String(temp))
startInd += 1
rangeInd += 1
}
for i in str {
let temp = Set(Array(i))
if temp.count == 3 {
count += 1
}
}
return count
}682. Baseball Game
Source: https://leetcode.com/problems/baseball-game/
Difficulty: Easy
func isInt(_ input: String) -> Bool {
if let value = Int(input) {
return true
}
return false
}
func isC(_ input: String) -> Bool {
if input == "C" {
return true
} else {
return false
}
}
func isD(_ input: String) -> Bool {
if input == "D" {
return true
} else {
return false
}
}
func isPlus(_ input: String) -> Bool {
if input == "+" {
return true
} else {
return false
}
}
func calPoints(_ ops: [String]) -> Int {
var stack = [Int]()
for i in ops {
if isInt(i) {
stack.append(Int(i)!)
} else if isC(i) {
stack.removeLast()
} else if isD(i) {
stack.append(stack[stack.count - 1] * 2)
} else if isPlus(i) {
stack.append(stack[stack.count - 1] + stack[stack.count - 2])
} else {
}
}
return stack.reduce(0) { $0 + $1 }
}1160. Find Words That Can Be Formed by Characters
Source: https://leetcode.com/problems/find-words-that-can-be-formed-by-characters/
Difficulty: Easy
func countCharacters(_ words: [String], _ chars: String) -> Int {
var count = 0
for i in words {
var char = Array(chars)
var temp = ""
for j in i {
if char.contains(j) {
temp.append(char.remove(at: char.firstIndex(of: j)!))
} else {
}
}
if temp.count == i.count {
count += i.count
}
}
return count
}1636. Sort Array by Increasing Frequency
Source: https://leetcode.com/problems/sort-array-by-increasing-frequency/
Difficulty: Easy
func frequencySort(_ nums: [Int]) -> [Int] {
var dict = [(Int, Int)]()
for i in nums {
dict.append((i, nums.filter { $0 == i }.count))
}
var result = [Int]()
dict.sort { $0.0 > $1.0 }
for i in dict.sorted { $0.1 < $1.1 } {
result.append(i.0)
}
return result
}1700. Number of Students Unable to Eat Lunch
Source: https://leetcode.com/problems/number-of-students-unable-to-eat-lunch/
Difficulty: Easy
func countStudents(_ students: [Int], _ sandwiches: [Int]) -> Int {
var queue = students
var stack = sandwiches
if queue.reduce(0) { $0 + $1 } == stack.reduce(0) { $0 + $1 } {
return 0
}
while !(queue.reduce(0) { $0 + $1 } == queue.count && stack.first! == 0) && !(queue.reduce(0) { $0 + $1 } == 0 && stack.first! == 1) {
if queue.first == stack.first {
queue.removeFirst()
stack.removeFirst()
} else {
queue.append(queue.removeFirst())
}
}
return queue.count
}136. Single Number
Source: https://leetcode.com/problems/single-number/
Difficulty: Easy
func singleNumber(_ nums: [Int]) -> Int {
var dict = [Int:Int]()
for i in nums {
dict[i, default: 0] += 1
}
var result = Int()
for (key, value) in dict {
if value == 1 {
result = key
}
}
return result
}1200. Minimum Absolute Difference
Source: https://leetcode.com/problems/minimum-absolute-difference/
Difficulty: Easy
func minimumAbsDifference(_ arr: [Int]) -> [[Int]] {
let sorted = arr.sorted(by: < )
var left = 0
var right = 1
var minValue = arr.max()!
var leftValue = 0
var rightValue = 1
var result = [[Int]]()
while right < sorted.count {
minValue = min(minValue, abs(sorted[right] - sorted[left]))
left += 1
right += 1
}
while rightValue < sorted.count {
if abs(sorted[rightValue] - sorted[leftValue]) == minValue {
result.append([sorted[leftValue], sorted[rightValue]])
}
leftValue += 1
rightValue += 1
}
return result
}496. Next Greater Element I
Source: https://leetcode.com/problems/next-greater-element-i/
Difficulty: Easy
func nextGreaterElement(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
var result = [Int]()
for i in nums1 {
let index = nums2.firstIndex(of: i)!
if nums2[index...].filter { $0 > i }.count != 0 {
result.append(nums2[index...].filter { $0 > i }[0])
} else {
result.append(-1)
}
}
return result
}824. Goat Latin
Source: https://leetcode.com/problems/goat-latin/
Difficulty: Easy
func toGoatLatin(_ sentence: String) -> String {
let compo = sentence.components(separatedBy: " ")
let condition: [Character] = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"]
var charArr = compo.map { Array($0) }
for i in 0..<charArr.count {
if condition.contains(charArr[i][0]) {
charArr[i].append("m")
charArr[i].append("a")
} else {
charArr[i].append(charArr[i].removeFirst())
charArr[i].append("m")
charArr[i].append("a")
}
}
for i in 0..<charArr.count {
charArr[i] += Array(repeating: "a", count: i + 1)
}
var result = ""
for i in charArr {
result.append(String(i))
result.append(" ")
}
result.removeLast()
return result
}349. Intersection of Two Arrays
Source: https://leetcode.com/problems/intersection-of-two-arrays/
Difficulty: Easy
func intersection(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
var set = Set<Int>()
for i in nums1 {
if nums2.contains(i) {
set.insert(i)
}
}
return Array(set)
}500. Keyboard Row
Source: https://leetcode.com/problems/keyboard-row/
Difficulty: Easy
func findWords(_ words: [String]) -> [String] {
let firstRow = Array("qwertyuiopQWERTYUIOP")
let secondRow = Array("asdfghjklASDFGHJKL")
let thirdRow = Array("zxcvbnmZXCVBNM")
var result = [String]()
for i in words {
var firstCount = 0
var secondCount = 0
var thirdCount = 0
for j in i {
if firstRow.contains(j) {
firstCount += 1
} else if secondRow.contains(j) {
secondCount += 1
} else if thirdRow.contains(j) {
thirdCount += 1
}
}
if firstCount == i.count || secondCount == i.count || thirdCount == i.count {
result.append(i)
}
}
return result
}1399. Count Largest Group
Source: https://leetcode.com/problems/count-largest-group/
Difficulty: Easy
func digitsSum(_ input: Int) -> Int {
let str = String(input)
var result = 0
for i in str {
result += Int(String(i))!
}
return result
}
func countLargestGroup(_ n: Int) -> Int {
var dict = [Int:Int]()
for i in 1...n {
dict[digitsSum(i), default: 0] += 1
}
let result = dict.sorted { $0.1 > $1.1 }
return result.filter { $0.1 == result[0].1 }.count
762. Prime Number of Set Bits in Binary Representation
Source: https://leetcode.com/problems/prime-number-of-set-bits-in-binary-representation/
Difficulty: Easy
func transformBinary(_ input: Int) -> String {
var temp = input
var result = ""
while temp != 0 {
let str = String(temp % 2)
result.append(str)
temp = temp / 2
}
return result
}
func countOne(_ input: String) -> Int {
var result = 0
for i in input {
if i == "1" {
result += 1
}
}
return result
}
func isPrime(_ input: Int) -> Bool {
var count = 0
for i in 1...input {
if input % i == 0 {
count += 1
}
}
if count == 2 {
return true
} else {
return false
}
}
func countPrimeSetBits(_ left: Int, _ right: Int) -> Int {
var count = 0
for i in left...right {
let binary = transformBinary(i)
let one = countOne(binary)
let primeBool = isPrime(one)
if primeBool == true {
count += 1
}
}
return count
}476. Number Complement
Source: https://leetcode.com/problems/number-complement/
Difficulty: Easy
func transformBinary(_ input: Int) -> String {
var temp = input
var result = ""
while temp != 0 {
let str = String(temp % 2)
if str == "0" {
result.append("1")
} else if str == "1" {
result.append("0")
}
temp = temp / 2
}
return result
}
func po(_ input: Int, _ count: Int) -> Int {
var result = 1
if count == 0 {
return result
}
for _ in 1...count {
result *= 2
}
return result
}
func transformInt(_ input: String) -> Int {
var result = 0
var arr = Array(input)
for i in 0..<input.count {
result += Int(String(arr[i]))! * po(2, i)
}
return result
}
func findComplement(_ num: Int) -> Int {
let binary = transformBinary(num)
return transformInt(binary)
}412. Fizz Buzz
Source: https://leetcode.com/problems/fizz-buzz/
Difficulty: Easy
func three(_ input: Int) -> Bool {
if input % 3 == 0 && input % 5 != 0 {
return true
} else {
return false
}
}
func five(_ input: Int) -> Bool {
if input % 3 != 0 && input % 5 == 0 {
return true
} else {
return false
}
}
func threeFive(_ input: Int) -> Bool {
if input % 3 == 0 && input % 5 == 0 {
return true
} else {
return false
}
}
func fizzBuzz(_ n: Int) -> [String] {
var result = [String]()
for i in 1...n {
if three(i) {
result.append("Fizz")
} else if five(i) {
result.append("Buzz")
} else if threeFive(i) {
result.append("FizzBuzz")
} else {
result.append("\(i)")
}
}
return result
}706. Design HashMap
Source: https://leetcode.com/problems/design-hashmap/
Difficulty: Easy
var myHashMap: [Int:Int]
/** Initialize your data structure here. */
init() {
myHashMap = [:]
}
/** value will always be non-negative. */
func put(_ key: Int, _ value: Int) {
myHashMap[key] = value
}
/** Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key */
func get(_ key: Int) -> Int {
return myHashMap.keys.contains(key) ? myHashMap[key]! : -1
}
/** Removes the mapping of the specified value key if this map contains a mapping for the key */
func remove(_ key: Int) {
myHashMap.removeValue(forKey: key)
}1408. String Matching in an Array
Source: https://leetcode.com/problems/string-matching-in-an-array/
Difficulty: Easy
func stringMatching(_ words: [String]) -> [String] {
var set = Set<String>()
for i in 0..<words.count {
let filter = words.filter { $0 != words[i] }
for j in filter {
if j.contains(words[i]) {
set.insert(words[i])
}
}
}
return Array(set)
}1394. Find Lucky Integer in an Array
Source: https://leetcode.com/problems/find-lucky-integer-in-an-array/
Difficulty: Easy
func findLucky(_ arr: [Int]) -> Int {
var dict = [Int:Int]()
var result = -1
for i in arr {
dict[i] = arr.filter { $0 == i }.count
}
for (key, value) in dict {
if key == value {
result = max(result, key)
}
}
return result
}1046. Last Stone Weight
Source: https://leetcode.com/problems/last-stone-weight/
Difficulty: Easy
func lastStoneWeight(_ stones: [Int]) -> Int {
var temp = stones
while temp.count > 1 {
let maximum = temp.remove(at: temp.firstIndex(of: temp.max()!)!)
let secondMaximum = temp.remove(at: temp.firstIndex(of: temp.max()!)!)
temp.append(maximum - secondMaximum)
}
return temp[0]
}1945. Sum of Digits of String After Convert
Source: https://leetcode.com/problems/sum-of-digits-of-string-after-convert/
Difficulty: Easy
func sToString(_ input: String) -> String {
let dict: [Character:String] = ["a":"1", "b":"2", "c":"3", "d":"4", "e":"5",
"f":"6", "g":"7", "h":"8", "i":"9", "j":"10",
"k":"11", "l":"12", "m":"13", "n":"14", "o":"15",
"p":"16", "q":"17", "r":"18", "s":"19", "t":"20",
"u":"21", "v":"22", "w":"23", "x":"24", "y":"25",
"z":"26"]
var str = ""
for i in input {
str.append(dict[i]!)
}
return str
}
func compress(_ input: String) -> String {
var intResult = 0
for i in input {
intResult += Int(String(i))!
}
return String(intResult)
}
func getLucky(_ s: String, _ k: Int) -> Int {
if k == 1 {
let temp = sToString(s)
var result = 0
for i in temp {
result += Int(String(i))!
}
return result
} else {
var firstStep = sToString(s)
for i in 1...k {
firstStep = compress(firstStep)
}
return Int(firstStep)!
}
}169. Majority Element
Source: https://leetcode.com/problems/majority-element/
Difficulty: Easy
func majorityElement(_ nums: [Int]) -> Int {
var dict = [Int:Int]()
for i in nums {
dict[i, default: 0] += 1
}
let sorted = dict.sorted { $0.1 > $1.1 }
return sorted[0].0
}242. Valid Anagram
Source: https://leetcode.com/problems/valid-anagram/
Difficulty: Easy
func isAnagram(_ s: String, _ t: String) -> Bool {
return String(s.sorted()) == String(t.sorted())
}1848. Minimum Distance to the Target Element
Source: https://leetcode.com/problems/minimum-distance-to-the-target-element/
Difficulty: Easy
func getMinDistance(_ nums: [Int], _ target: Int, _ start: Int) -> Int {
var candidate = [Int]()
for i in 0..<nums.count {
if nums[i] == target {
candidate.append(abs(i - start))
}
}
return candidate.min()!
}1287. Element Appearing More Than 25% In Sorted Array
Source: https://leetcode.com/problems/element-appearing-more-than-25-in-sorted-array/
Difficulty: Easy
func findSpecialInteger(_ arr: [Int]) -> Int {
var dictCount = [Int:Int]()
for i in arr {
dictCount[i, default: 0] += 1
}
let sorted = dictCount.sorted { $0.1 > $1.1 }
return sorted[0].0
}258. Add Digits
Source: https://leetcode.com/problems/add-digits/
Difficulty: Easy
func addDigits(_ num: Int) -> Int {
var strNum = String(num)
while strNum.count > 1 {
let charArr = Array(strNum)
var temp = 0
for i in charArr {
temp += Int(String(i))!
}
strNum = String(temp)
}
return Int(strNum)!
}1869. Longer Contiguous Segments of Ones than Zeros
Source: https://leetcode.com/problems/longer-contiguous-segments-of-ones-than-zeros/
Difficulty: Easy
func checkZeroOnes(_ s: String) -> Bool {
let oneArr = s.components(separatedBy: "0")
let zeroArr = s.components(separatedBy: "1")
var countOne = [Int]()
var countZero = [Int]()
for i in oneArr {
countOne.append(i.count)
}
for i in zeroArr {
countZero.append(i.count)
}
return countOne.max()! > countZero.max()!
}283. Move Zeroes
Source: https://leetcode.com/problems/move-zeroes/
Difficulty: Easy
func moveZeroes(_ nums: inout [Int]) {
if nums.filter { $0 == 0 }.count == 0 {
} else {
let zeroCount = nums.filter { $0 == 0 }.count
nums = nums.filter { $0 != 0 }
for _ in 1...zeroCount {
nums.append(0)
}
}
}1624. Largest Substring Between Two Equal Characters
Source: https://leetcode.com/problems/largest-substring-between-two-equal-characters/
Difficulty: Easy
func maxLengthBetweenEqualCharacters(_ s: String) -> Int {
let char = Array(s)
var result = 0
var ind = 0
while ind < char.count {
result = max(char.lastIndex(of: char[ind])! - ind, result)
ind += 1
}
return result - 1
}389. Find the Difference
Source: https://leetcode.com/problems/find-the-difference/
Difficulty: Easy
func findTheDifference(_ s: String, _ t: String) -> Character {
var charS = Array(s)
var charT = Array(t)
while charT.count != 1 {
for i in charS {
if charT.contains(i) {
charS.remove(at: charS.firstIndex(of: i)!)
charT.remove(at: charT.firstIndex(of: i)!)
}
}
}
return charT[0]
}217. Contains Duplicate
Source: https://leetcode.com/problems/contains-duplicate/
Difficulty: Easy
func containsDuplicate(_ nums: [Int]) -> Bool {
var dict = [Int:Int]()
var count = 0
for i in nums {
dict[i, default: 0] += 1
}
for (key, value) in dict {
if value > 1 {
count += 1
}
}
return count != 0
}896. Monotonic Array
Source: https://leetcode.com/problems/monotonic-array/
Difficulty: Easy
func isMonotonic(_ nums: [Int]) -> Bool {
let decreasing = nums.sorted(by: > )
let increasing = nums.sorted(by: < )
if nums == decreasing || nums == increasing {
return true
} else {
return false
}
}1422. Maximum Score After Splitting a String
Source: https://leetcode.com/problems/maximum-score-after-splitting-a-string/
Difficulty: Easy
func maxScore(_ s: String) -> Int {
let char = Array(s)
var ind = 0
var result = 0
while ind < s.count - 1 {
let zero = char[0...ind].filter { $0 == "0" }.count
let one = char[(ind + 1)...].filter { $0 == "1" }.count
result = max(zero + one, result)
ind += 1
}
return result
}268. Missing Number
Source: https://leetcode.com/problems/missing-number/
Difficulty: Easy
func missingNumber(_ nums: [Int]) -> Int {
let count = nums.count
var condition = 0
for i in 0...count {
condition += i
}
return condition - nums.reduce(0) { $0 + $1 }
}1317. Convert Integer to the Sum of Two No-Zero Integers
Source: https://leetcode.com/problems/convert-integer-to-the-sum-of-two-no-zero-integers/
Difficulty: Easy
func isContainZero(_ input: Int) -> Bool {
let char = Array(String(input))
return char.contains("0")
}
func getNoZeroIntegers(_ n: Int) -> [Int] {
var one = 1
var two = n - 1
var result = [Int]()
while one < n {
if !isContainZero(one) && !isContainZero(two) {
result = [one, two]
break
} else {
result = []
}
one += 1
two -= 1
}
return result
}704. Binary Search
Source: https://leetcode.com/problems/binary-search/
Difficulty: Easy
func search(_ nums: [Int], _ target: Int) -> Int {
var result = -1
for i in 0..<nums.count {
if nums[i] == target {
result = i
}
}
return result
}1539. Kth Missing Positive Number
Source: https://leetcode.com/problems/kth-missing-positive-number/
Difficulty: Easy
func findKthPositive(_ arr: [Int], _ k: Int) -> Int {
var temp = [Int]()
for i in 1...(arr.count + k) {
if !arr.contains(i) {
temp.append(i)
}
}
return temp[k - 1]
}520. Detect Capital
Source: https://leetcode.com/problems/detect-capital/
Difficulty: Easy
func isAllUpper(_ input: String) -> Bool {
if input == input.uppercased() {
return true
} else {
return false
}
}
func isAllLower(_ input: String) -> Bool {
if input == input.lowercased() {
return true
} else {
return false
}
}
func isFirstUpper(_ input: String) -> Bool {
let char = Array(input)
if String(char[0]) == String(char[0]).uppercased() && String(char[1...]) == String(char[1...]).lowercased() {
return true
} else {
return false
}
}
func detectCapitalUse(_ word: String) -> Bool {
if isAllUpper(word) || isAllLower(word) || isFirstUpper(word) {
return true
} else {
return false
}
}1523. Count Odd Numbers in an Interval Range
Source: https://leetcode.com/problems/count-odd-numbers-in-an-interval-range/
Difficulty: Easy
func countOdds(_ low: Int, _ high: Int) -> Int {
let differ = high - low
if high % 2 == 0 && low % 2 == 0 {
return differ / 2
} else {
return differ / 2 + 1
}
}121. Best Time to Buy and Sell Stock
Source: https://leetcode.com/problems/best-time-to-buy-and-sell-stock/
Difficulty: Easy
func maxProfit(_ prices: [Int]) -> Int {
var a = 0
var minP = prices.max()!
for i in prices {
minP = min(minP, i)
a = max(a, i - minP)
}
return a
}1089. Duplicate Zeros
Source: https://leetcode.com/problems/duplicate-zeros/
Difficulty: Easy
func duplicateZeros(_ arr: inout [Int]) {
var ind = 0
while ind < arr.count {
if arr[ind] == 0 {
arr.insert(0, at: ind + 1)
arr.removeLast()
ind += 2
} else {
ind += 1
}
}
}225. Implement Stack using Queues
Source: https://leetcode.com/problems/implement-stack-using-queues/
Difficulty: Easy
var stack = [Int]()
/** Initialize your data structure here. */
init() {
stack = []
}
/** Push element x onto stack. */
func push(_ x: Int) {
stack.append(x)
}
/** Removes the element on top of the stack and returns that element. */
func pop() -> Int {
return stack.isEmpty ? -1 : stack.removeLast()
}
/** Get the top element. */
func top() -> Int {
return stack.isEmpty ? -1 : stack.last!
}
/** Returns whether the stack is empty. */
func empty() -> Bool {
return stack.isEmpty
}1. Two Sum
Source: https://leetcode.com/problems/two-sum/
Difficulty: Easy
func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
var result = [Int]()
for i in 0..<nums.count {
for j in (i+1)..<nums.count {
if nums[i] + nums[j] == target {
result = [i, j]
}
}
}
return result
}819. Most Common Word
Source: https://leetcode.com/problems/most-common-word/
Difficulty: Easy
func mostCommonWord(_ paragraph: String, _ banned: [String]) -> String {
var separate = paragraph.lowercased().split { !$0.isLetter }
var arr = [String]()
for i in separate {
arr.append(String(i))
}
var setForKey = Set(arr)
var dict = [(String, Int)]()
for i in setForKey {
dict.append((i, arr.filter { $0 == i }.count))
}
for i in banned {
dict = dict.filter { $0.0 != i }
}
return dict.sorted { $0.1 > $1.1 }[0].0
}167. Two Sum II - Input array is sorted
Source: https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/
Difficulty: Easy
func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
var left = 0
var right = numbers.count - 1
var result = [Int]()
while numbers[left] + numbers[right] != target {
if numbers[left] + numbers[right] < target {
left += 1
} else if numbers[left] + numbers[right] > target {
right -= 1
}
}
result.append(left + 1)
result.append(right + 1)
return result
}747. Largest Number At Least Twice of Others
Source: https://leetcode.com/problems/largest-number-at-least-twice-of-others/
Difficulty: Easy
func dominantIndex(_ nums: [Int]) -> Int {
let filter = nums.filter { $0 != nums.max()! }
var firstIndOfMax = nums.firstIndex(of: nums.max()!)!
for i in filter {
if i * 2 > nums.max()! {
firstIndOfMax = -1
}
}
return firstIndOfMax
}234. Palindrome Linked List
Source: https://leetcode.com/problems/palindrome-linked-list/
Difficulty: Easy
func isPalindrome(_ head: ListNode?) -> Bool {
if head == nil {
return true
}
var head = head
var array = [Int]()
while head != nil {
array.append(head!.val)
head = head!.next
}
if array != array.reversed() {
return false
}
return true
}231. Power of Two
Source: https://leetcode.com/problems/power-of-two/
Difficulty: Easy
func isPowerOfTwo(_ n: Int) -> Bool {
if n == 0 {
return false
}
var temp = n
var arr = [Int]()
while temp != 0 {
arr.append(temp % 2)
temp = temp / 2
}
return arr[arr.count - 1] == 1 && arr.reduce(0) { $0 + $1 } == 1
}326. Power of Three
Source: https://leetcode.com/problems/power-of-three/
Difficulty: Easy
func isPowerOfThree(_ n: Int) -> Bool {
if n == 0 {
return false
}
var temp = n
var arr = [Int]()
while temp != 0 {
arr.append(temp % 3)
temp = temp / 3
}
return arr[arr.count - 1] == 1 && arr.reduce(0) { $0 + $1 } == 1
}342. Power of Four
Source: https://leetcode.com/problems/power-of-four/
Difficulty: Easy
func isPowerOfFour(_ n: Int) -> Bool {
if n <= 0 {
return false
}
var num = n
var rem = 0
while (num > 1) {
rem = num % 4
if rem != 0 {
return false
}
num = num/4
}
return true
}20. Valid Parentheses
Source: https://leetcode.com/problems/valid-parentheses/
Difficulty: Easy
func isValid(_ s: String) -> Bool {
let dict: [Character:Character] = ["(":")", "{":"}", "[":"]"]
var stack = [Character]()
for i in s {
if dict.keys.contains(i) {
stack.append(i)
} else if stack.isEmpty || i != dict[stack.removeLast()] {
return false
}
}
return stack.isEmpty
}125. Valid Palindrome
Source: https://leetcode.com/problems/valid-palindrome/
Difficulty: Easy
func isPalindrome(_ s: String) -> Bool {
let charArray = s.lowercased().filter { $0.isLetter == true || $0.isNumber == true }
if String(charArray) == String(charArray.reversed()) {
return true
} else {
return false
}
}507. Perfect Number
Source: https://leetcode.com/problems/perfect-number/
Difficulty: Easy
func checkPerfectNumber(_ num: Int) -> Bool {
var temp = [Int]()
for i in 1...num {
if num % i == 0 {
temp.append(i)
}
}
temp.removeLast()
return temp.reduce(0) { $0 + $1 } == num
}414. Third Maximum Number
Source: https://leetcode.com/problems/third-maximum-number/
Difficulty: Easy
func thirdMax(_ nums: [Int]) -> Int {
let set = Set(nums)
let sorted = Array(set.sorted { $0 > $1 })
if sorted.count > 2 {
return sorted[2]
} else {
return sorted[0]
}
}