토마토

문제

토마토

풀이

맨 처음 익어있는 토마토를 전부 큐에 넣은 후 BFS를 돌리면 됩니다. 숨바꼭질과 비슷하게 방문 처리를 시간으로 하면 됩니다.

코드

Python

import sys
from collections import deque
 
input = lambda: sys.stdin.readline().rstrip()
 
 
dx = [1, -1, 0, 0]
dy = [0, 0, 1, -1]
 
m, n = map(int, input().split())
 
time = [[-1] * m for _ in range(n)]
queue = deque()
for i in range(n):
    for j, state in enumerate(map(int, input().split())):
        if state == 1:
            time[i][j] = 0
            queue.append((i, j))
        elif state == -1:
            time[i][j] = 0
 
while queue:
    x, y = queue.popleft()
 
    for k in range(4):
        nx = x + dx[k]
        ny = y + dy[k]
 
        if nx < 0 or nx >= n or ny < 0 or ny >= m:
            continue
 
        if time[nx][ny] == -1:
            time[nx][ny] = time[x][y] + 1
            queue.append((nx, ny))
 
answer = 0
for i in range(n):
    for j in range(m):
        if time[i][j] == -1:
            print(-1)
            sys.exit(0)
        answer = max(answer, time[i][j])
 
print(answer)

C++

#include <bits/stdc++.h>
using namespace std;
 
array<int, 4> dx = {1, -1, 0, 0};
array<int, 4> dy = {0, 0, 1, -1};
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
 
    int m, n;
    cin >> m >> n;
 
    vector<vector<int>> time(n, vector<int>(m, -1));
    queue<pair<int, int>> q;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            int state;
            cin >> state;
            if (state == 1) {
                time[i][j] = 0;
                q.push(pair(i, j));
            } else if (state == -1)
                time[i][j] = 0;
        }
    }
 
    while (not q.empty()) {
        auto [x, y] = q.front();
        q.pop();
 
        for (int k = 0; k < 4; k++) {
            int nx = x + dx[k], ny = y + dy[k];
 
            if (nx < 0 or nx >= n or ny < 0 or ny >= m)
                continue;
 
            if (time[nx][ny] == -1) {
                time[nx][ny] = time[x][y] + 1;
                q.push(pair(nx, ny));
            }
        }
    }
 
    int answer = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            if (time[i][j] == -1) {
                cout << -1;
                return 0;
            }
 
            answer = max(answer, time[i][j]);
        }
    }
 
    cout << answer;
    return 0;
}

Java

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;
 
public class Main {
    static int dx[] = { 1, -1, 0, 0 }, dy[] = { 0, 0, 1, -1 };
 
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
 
        StringTokenizer tk = new StringTokenizer(br.readLine());
        int m = Integer.parseInt(tk.nextToken()), n = Integer.parseInt(tk.nextToken());
 
        int time[][] = new int[n][m];
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                time[i][j] = -1;
 
        Queue<Pair> queue = new LinkedList<>();
        for (int i = 0; i < n; i++) {
            tk = new StringTokenizer(br.readLine());
            for (int j = 0; j < m; j++) {
                int state = Integer.parseInt(tk.nextToken());
 
                if (state == 1) {
                    time[i][j] = 0;
                    queue.add(new Pair(i, j));
                } else if (state == -1)
                    time[i][j] = 0;
            }
        }
 
        while (!queue.isEmpty()) {
            Pair p = queue.poll();
            int x = p.first, y = p.second;
 
            for (int k = 0; k < 4; k++) {
                int nx = x + dx[k], ny = y + dy[k];
 
                if (nx < 0 || nx >= n || ny < 0 || ny >= m)
                    continue;
 
                if (time[nx][ny] == -1) {
                    time[nx][ny] = time[x][y] + 1;
                    queue.add(new Pair(nx, ny));
                }
            }
        }
 
        int answer = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (time[i][j] == -1) {
                    bw.write("-1");
                    bw.close();
                    return;
                }
 
                answer = Math.max(answer, time[i][j]);
            }
        }
 
        bw.write(answer + "");
        bw.close();
    }
}
 
class Pair {
    int first, second;
 
    Pair(int first, int second) {
        this.first = first;
        this.second = second;
    }
}