图论20（Leetcode1254.统计封闭岛屿的数目）

代码：

class Solution {
    static int[][] dirs = {{1,0},{-1,0},{0,1},{0,-1}};
    public int closedIsland(int[][] grid) {
        int num = 0; 
        for(int i=0;i
            for(int j=0;j0].length;j++){
                if(grid[i][j]==0){
                    int[] start = {i,j};
                    if(getIsland(start,grid)){
                        num++;
                    }
                }
            }
        }
        return num;
    }
    private boolean getIsland(int[] start,int[][] grid){
        boolean flag = true;
        grid[start[0]][start[1]] = -1;
        for(int i=0;i
            int x = start[0] + dirs[i][0];
            int y = start[1] + dirs[i][1];
            if(x<0||x==grid.length||y<0||y==grid[0].length)flag = false;
            if(x>=0&&x=0&&y0].length&&grid[x][y]==0){
                int[] cur = {x,y};
                if(flag==true){
                    flag = getIsland(cur,grid);
                }else{
                    getIsland(cur,grid);
                }
                
            }
        }
        return flag;
    }
}