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```class Solution {
public:
void rot(vector<vector<int>>& grid,int x,int y,int r,int c,queue<pair<int,int>>&q){
if(x-1>=0 && grid[x-1][y]==1) {grid[x-1][y]=2; q.push({x-1,y});}
if(x+1<r && grid[x+1][y]==1) {grid[x+1][y]=2; q.push({x+1,y});}
if(y+1<c && grid[x][y+1]==1) {grid[x][y+1]=2; q.push({x,y+1});}
if(y-1>=0 && grid[x][y-1]==1) {grid[x][y-1]=2; q.push({x,y-1});}
//fresh=false;
//if((x-1<0 || grid[x-1][y]==0 ) && (x+1>=r || grid[x+1][y]==0) && (y-1<0 || grid[x][y-1]==0) && (y+1>=c || grid[x][y+1]==0)) fresh =true;
}

int orangesRotting(vector<vector<int>>& grid) {
int r=grid.size(), c=grid[0].size();
if(r==1 && c==1) {
if(grid[0][0]==1) return -1;
return 0;
}

queue<pair<int,int>> q; //holds rotten oragnes coordinates
int time=0;
for(int i=0;i<r;i++){
for(int j=0;j<c;j++){
if(grid[i][j]==2) q.push({i,j});
}
}
while(!q.empty()){
int s=q.size();
while(s--){ //process one time period
pair<int,int> p =q.front();
q.pop();
int x=p.first, y=p.second;
//bool fresh =false;
rot(grid,x,y,r,c,q);

}
time++;
}
for(int i=0;i<r;i++){
for(int j=0;j<c;j++){
if(grid[i][j]==1) return -1;
}
}
if(time>0) return time-1;
else return 0;
}
};```