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
        int res = 0;
        boolean[][] isVisited = new boolean[grid.length][grid[0].length];
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (!isVisited[i][j] && grid[i][j] == '1') {
                    res++;
                    dfs(grid, isVisited, i, j); //标记
                }
            }
        }
        return res;
    }
    private void dfs(char[][] grid, boolean[][] isVisited, int i, int j) { //标记
        int n = grid.length, m = grid[0].length;
        isVisited[i][j] = true;
        if (i - 1 >= 0 && grid[i - 1][j] == '1' && !isVisited[i - 1][j])
            dfs(grid, isVisited, i - 1, j); //左
        if (i + 1 < n && grid[i + 1][j] == '1' && !isVisited[i + 1][j])
            dfs(grid, isVisited, i + 1, j); //右
        if (j - 1 >= 0 && grid[i][j - 1] == '1' && !isVisited[i][j - 1])
            dfs(grid, isVisited, i, j - 1); //上
        if (j + 1 < m && grid[i][j + 1] == '1' && !isVisited[i][j + 1])
            dfs(grid, isVisited, i, j + 1); //下
    }
}