[백준] 2644 - Swift

코드

import Foundation

let input = Int(readLine()!)!
let twoNum = Array(readLine()!).split(separator: " ").map{Int(String($0))!}
let line = Int(readLine()!)!

var grid = [Int:[Int]]()

for _ in 0..<line {
    let arr = Array(readLine()!).split(separator: " ").map{Int(String($0))!}
    let a = arr[0]
    let b = arr[1]
    
    if grid[a] == nil {
        grid[a] = [b]
    } else {
        grid[a]?.append(b)
    }
    
    if grid[b] == nil {
        grid[b] = [a]
    } else {
        grid[b]?.append(a)
    }
}

var visited = Array(repeating: false, count: input + 1)
var queue = [(twoNum[0],0)]
visited[twoNum[0]] = true
var answer = -1

while !queue.isEmpty {
    let now = queue.removeFirst()
    
    if now.0 == twoNum[1] {
        answer = now.1
    }
    
    if let person = grid[now.0] {
        for i in person {
            if !visited[i] {
                visited[i] = true
                queue.append((i,now.1+1))
            }
        }
    }
}

print(answer)

회고

• bfs 문제였다
• bfs/dfs 문제들만 푸니까 조금씩 이해가기 시작한다