腐烂的橘子

题目描述：力扣

解题思路：

使用BFS，具体参考：https://leetcode-cn.com/problems/rotting-oranges/solution/li-qing-si-lu-wei-shi-yao-yong-bfsyi-ji-ru-he-xie-/

class Solution {
    public static int orangesRotting(int[][] grid) {
        int row = grid.length;
        int col = grid[0].length;
        int count = 0;
        int res = 0;
        Queue<int[]> queue = new LinkedList<>();
        for(int i = 0; i < row; i++){
            for(int j = 0 ; j < col; j++){
                if(grid[i][j]==1){
                    count++;
                }
                else if(grid[i][j]==2){
                    queue.add(new int[]{i,j});
                }
            }
        }

        while(count>0&&!queue.isEmpty()){
            int num = queue.size();
            if(num == 0)
            	return 0;
            res++;
            for(int i = 0; i< num;i++){
            	int[] a = queue.poll();
            	int x = a[0];
            	int y = a[1];
            	if(x>0&&grid[x-1][y]==1){
            		grid[x-1][y]=2;
            		queue.add(new int[]{x-1,y});
            		count--;
            	}
            	if(y<col-1 && grid[x][y+1]==1){
            		grid[x][y+1]=2;
            		queue.add(new int[]{x,y+1});
            		count--;
            	}
            	if(x<row-1 && grid[x+1][y]==1){
            		grid[x+1][y]=2;
            		queue.add(new int[]{x+1,y});
            		count--;
            	}
            	if(y>0 && grid[x][y-1]==1){
            		grid[x][y-1]=2;
            		queue.add(new int[]{x, y-1});
            		count--;
            	}
            }
        }
        if(count>0)
        	return -1;
        else{
        	return res;
        }

    }
}