int orangesRotting(vector<vector<int>>& grid) {
        int n= grid.size();
        int t;
        int m = grid[0].size();
        int vis[n][m];
        queue<pair<pair<int,int>,int>> q;
        for(int i=0;i<n;++i)
        {
            for(int j=0;j<m;++j)
            {
                if(grid[i][j]==2){
                q.push({{i,j},0});
                vis[i][j]=2;}
                else
                    vis[i][j]=0;
            }
        }
        int tm=0;
            while(!q.empty())
            {
                int r = q.front().first.first;
                int c = q.front().first.second;
                 t = q.front().second;
                 tm = max(t,tm);
                q.pop();
                int drow[] = {0,1,-1,0};
                int dcol[] = {1,0,0,-1};
                for(int i=0;i<4;++i)
                {
                    int nr = r+drow[i];
                    int nc = c+dcol[i];
                    if(nr>=0 && nr<n && nc>=0 && nc<m && vis[nr][nc]!=2 && grid[nr][nc]==1)
                    {
                        q.push({{nr,nc},t+1});
                        vis[nr][nc]=2;
                    }
                    
                }
            }
        
        for(int i=0;i<n;++i)
        {
            for(int j=0;j<m;++j)
            {
                if(grid[i][j]==1 && vis[i][j]!=2)
                return -1; 
            }

        }

        return tm;
    }