In a given grid, each cell can have one of three values:
the value 0 representing an empty cell;
the value 1 representing a fresh orange;
the value 2 representing a rotten orange.
Every minute, any fresh orange that is adjacent (4-directionally) to a rotten orange becomes rotten.
Return the minimum number of minutes that must elapse until no cell has a fresh orange. If this is impossible, return -1 instead
Example 1:
Input: [[2,1,1],[1,1,0],[0,1,1]]
Output: 4
Example 2:
Input: [[2,1,1],[0,1,1],[1,0,1]]
Output: -1
Explanation: The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally.
Example 3:
Input: [[0,2]]
Output: 0
Explanation: Since there are already no fresh oranges at minute 0, the answer is just 0.
Note:
1 <= grid.length <= 10
1 <= grid[0].length <= 10
grid[i][j] is only 0, 1, or 2
classSolution{publicintorangesRotting(int[][] grid){if(grid == null || grid.length ==0)return0;int rows = grid.length;int cols = grid[0].length;
Queue<int[]> queue =newLinkedList<>();int count_fresh =0;//Put the position of all rotten oranges in queue//count the number of fresh orangesfor(int i =0; i < rows ; i++){for(int j =0; j < cols ; j++){if(grid[i][j]==2){
queue.offer(newint[]{i , j});}elseif(grid[i][j]==1){
count_fresh++;}}}//if count of fresh oranges is zero --> return 0 if(count_fresh ==0)return0;int count =0;int[][] dirs ={{1,0},{-1,0},{0,1},{0,-1}};//bfs starting from initially rotten orangeswhile(!queue.isEmpty()){++count;int size = queue.size();for(int i =0; i < size ; i++){int[] point = queue.poll();for(int dir[]: dirs){int x = point[0]+ dir[0];int y = point[1]+ dir[1];//if x or y is out of bound//or the orange at (x , y) is already rotten//or the cell at (x , y) is empty//we do nothingif(x <0|| y <0|| x >= rows || y >= cols || grid[x][y]==0|| grid[x][y]==2)continue;//mark the orange at (x , y) as rotten
grid[x][y]=2;//put the new rotten orange at (x , y) in queue
queue.offer(newint[]{x , y});//decrease the count of fresh oranges by 1
count_fresh--;}}}return count_fresh ==0? count-1:-1;}}