题解 | #岛屿数量#

import java.util.*;

 //计算路径的个数，DFS最优，不推荐BFS
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) {
        int n = grid.length;
        //空矩阵
        if (n == 0) return 0;

        int m = grid[0].length;
        //岛屿计数
        int count = 0;
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (grid[i][j] == '1') {
                    dfs(grid, i, j);//将与这个1相邻的所有1置为0
                    count++;
                }
            }
        }
        return count;
    }

    private void dfs(char[][] grid, int i, int j) {
        grid[i][j] = '0';
        int n = grid.length;
        int m = grid[0].length;
        if (i - 1 >= 0 && grid[i - 1][j] == '1') {
            dfs(grid, i - 1, j);
        }
        if (i + 1 < n && grid[i + 1][j] == '1') {
            dfs(grid, i + 1, j);
        }
        if (j - 1 >= 0 && grid[i][j - 1]  == '1') {
            dfs(grid, i, j - 1);
        }
        if (j + 1 < m && grid[i][j + 1] == '1') {
            dfs(grid, i, j + 1);
        }
    }
}