994

class Solution {
public:
    int orangesRotting(vector<vector<int>>& grid) {
        queue<pair<int, int>> q;
        int rows = grid.size(), cols=grid[0].size();

        for(int i=0; i<rows; i++)
            for(int j=0; j<cols; j++)
                if(grid[i][j] == 2)
                    q.push({i, j});

        int minutes = 0;
        int dir[4][2] = {{0,1}, {0,-1}, {1,0}, {-1,0}};

        while(!q.empty()){
            int sz = q.size();
            int count = 0;
            for(int i=0; i<sz; i++){
                auto p = q.front();
                q.pop();
                for(int j=0; j<4; j++){
                    int nextX = p.first+dir[j][0], nextY = p.second+dir[j][1];
                    if(nextX < 0 || nextX >= rows || nextY < 0  || nextY >= cols || grid[nextX][nextY] != 1)
                        continue;
                    grid[nextX][nextY] = 2;
                    q.push({nextX, nextY});
                    count++;
                }
            }
            if(count)
                minutes++;
        }

        bool allRotten = true;
        for(int i=0; i<rows; i++)
            for(int j=0; j<cols; j++)
                if(grid[i][j] == 1)
                    allRotten = false;

        return allRotten ? minutes : -1;
    }
};