[백준 7576] 토마토 (DFS/BFS)

7576번: 토마토 (acmicpc.net)

7576번: 토마토

 

내풀이

#include <cstdio>
#include <queue>
using namespace std;
int a[1000][1000];
int d[1000][1000];
int dx[] = {0,0,1,-1};
int dy[] = {1,-1,0,0};
int main() {
    int n,m;
    scanf("%d %d",&n,&m);
    queue<pair<int,int>> q;
    for (int i=0; i<n; i++) {
        for (int j=0; j<m; j++) {
            scanf("%d",&a[i][j]);
            d[i][j] = -1;
            if (a[i][j] == 1) {
                q.push(make_pair(i,j));
                d[i][j] = 0;
            }
        }
    }
    while (!q.empty()) {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        for (int k=0; k<4; k++) {
            int nx = x+dx[k];
            int ny = y+dy[k];
            if (0 <= nx && nx < n && 0 <= ny && ny < m) {
                if (a[nx][ny] == 0 && d[nx][ny] == -1) {
                    d[nx][ny] = d[x][y] + 1;
                    q.push(make_pair(nx,ny));
                }
            }
        }
    }
    int ans = 0;
    for (int i=0; i<n; i++) {
        for (int j=0; j<m; j++) {
            if (ans < d[i][j]) {
                ans = d[i][j];
            }
        }
    }
    for (int i=0; i<n; i++) {
        for (int j=0; j<m; j++) {
            if (a[i][j] == 0 && d[i][j] == -1) {
                ans = -1;
            }
        }
    }

    printf("%d\n",ans);
    return 0;
}

 

정답풀이

#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
int board[1002][1002];
int dist[1002][1002];
int n,m;
int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};
int main(void){
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> m >> n;
  queue<pair<int,int> > Q;
  for(int i = 0; i < n; i++){
    for(int j = 0; j < m; j++){
      cin >> board[i][j];
      if(board[i][j] == 1)
        Q.push({i,j});
      if(board[i][j] == 0)
        dist[i][j] = -1;
    }
  }
  while(!Q.empty()){
    auto cur = Q.front(); Q.pop();
    for(int dir = 0; dir < 4; dir++){
      int nx = cur.X + dx[dir];
      int ny = cur.Y + dy[dir];
      if(nx < 0 || nx >= n || ny < 0 || ny >= m) continue;
      if(dist[nx][ny] >= 0) continue;
      dist[nx][ny] = dist[cur.X][cur.Y]+1;
      Q.push({nx,ny});
    }
  }
  int ans = 0;
  for(int i = 0; i < n; i++){
    for(int j = 0; j < m; j++){
      if(dist[i][j] == -1){
        cout << -1;
        return 0;
      }
      ans = max(ans, dist[i][j]);
    }
  }
  cout << ans;
}