题解 | #岛屿数量#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 判断岛屿数量
     * @param grid char字符型二维数组 
     * @return int整型
     */
    private void dfsZero(char[][] grid, int i, int j){
        int m = grid.length;
        int n = grid[0].length;
        grid[i][j] = '0';

        if(i-1>=0 && grid[i-1][j]=='1')
            dfsZero(grid, i-1, j);
        if(i+1<m && grid[i+1][j]=='1')
            dfsZero(grid, i+1, j);
        if(j-1>=0 && grid[i][j-1]=='1')
            dfsZero(grid, i, j-1);
        if(j+1<n && grid[i][j+1]=='1')
            dfsZero(grid, i, j+1);
    }
    
    public int solve (char[][] grid) {
        // write code here
        if(grid.length==0) return 0;
        int m = grid.length;
        int n = grid[0].length;
        int island = 0;

        for(int i=0; i<m;i++){
            for(int j=0;j<n;j++){
                if(grid[i][j]=='1'){
                    island++;
                    dfsZero(grid, i, j);
                }
            }
        }

        return island;

    }
}

递归的思想不止能用于树