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
     */
    public int solve (char[][] grid) {
        // write code here
        // 解题思路：
        // 1.遍历二维数组，如果是1，则把它消除，同时把它前后左右的1都消除
        // 2.递归，从前后左右开始分别把各自前后左右的都消除
        int m = grid.length;
        int n = grid[0].length;
        int count = 0;

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

        return count;
    }

    private void clear(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') {
            clear(grid, i - 1, j);
        }


        if (i + 1 < m && grid[i + 1][j] == '1') {
            clear(grid, i + 1, j);
        }


        if (j - 1 >= 0 && grid[i][j - 1] == '1') {
            clear(grid, i, j - 1);
        }


        if (j + 1 < n && grid[i][j + 1] == '1') {
            clear(grid, i, j + 1);
        }
    }
}