LeetCode994. 腐烂的橘子

//994. 腐烂的橘子
class Solution {
public:
  vector<vector<int>>s;
  vector<vector<int>>f;
  const int inf = 0x3f3f3f3f;
  int m, n;
  bool legal(int i, int j) {
    return (0 <= i && i < n && 0 <= j && j < m);
  }
  void bfs(int i, int j) {
    queue<pair<int, int>>p;
    p.push({ i,j });
    int cnt = -1;
    while (p.size()) {
      cnt++;
      queue<pair<int, int>>q;
      while (p.size()) {
        auto t = p.front(); p.pop();
        int x = t.first;
        int y = t.second;
        if (legal(x, y)) {
          if (s[x][y]) {
            s[x][y] = 0;
            f[x][y] = min(f[x][y], cnt);
            q.push({ x - 1,y });
            q.push({ x,y - 1 });
            q.push({ x + 1,y });
            q.push({ x,y + 1 });
          }
        }
      }
      p = q;
    }
  }
  int orangesRotting(vector<vector<int>>& grid) {
    n = grid.size();
    m = grid[0].size();
    vector<vector<int>>ft(n, vector<int>(m, inf));
    f = ft;
    for (int i = 0; i < n; i++)
      for (int j = 0; j < m; j++)
        if (grid[i][j] == 2) {
          s = grid;
          f[i][j] = 0;
          bfs(i, j);
        }
    int ans = 0;
    for (int i = 0; i < n; i++)
      for (int j = 0; j < m; j++)
        if (grid[i][j]) ans = max(ans, f[i][j]);
    if (ans == inf) return -1;
    return ans;
  }
};