https://leetcode.com/problems/palindrome-number/description/
9. Palindrome Number
Given an integer x, return true if x is a palindrome, and false otherwise.
Examples
Example 1:
Input: x = 121
Output: true
Explanation: 121 reads as 121 from left to right and from right to left.
Example 2:
Input: x = -121
Output: false
Explanation: From left to right, it reads -121. From right to left, it becomes 121-. Therefore it is not a palindrome.
Example 3:
Input: x = 10
Output: false
Explanation: Reads 01 from right to left. Therefore it is not a palindrome.
Constraints:
-231 <= x <= 231 - 1
Follow up
Could you solve it without converting the integer to a string?
풀이
풀이1
/**
* @param {number} x
* @return {boolean}
*/
var isPalindrome = function(x) {
if(x < 0) {
return false;
}
if(x === 0) {
return true;
}
const stringArr = String(x).split('');
const reversedStringArr = stringArr.reverse();
const reversedNumber = Number(reversedStringArr.join(''));
return x === reversedNumber;
};시간 복잡도
T(N) = O(logN)
풀이2
/**
* @param {number} x
* @return {boolean}
*/
var isPalindrome = function(x) {
if(x < 0) {
return false;
}
if(x === 0) {
return true;
}
const digit = Math.floor(Math.log10(x)+1);
let remainder = x;
let reversedNumber = "";
for(let i = digit - 1; i >= 0; i--) {
reversedNumber = Math.floor(remainder / Math.pow(10, i)) + reversedNumber;
remainder = remainder % Math.pow(10, i);
}
return x + "" === reversedNumber;
};