【LeeCode】695. 岛屿的最大面积

【题目描述】

给你一个大小为 m x n 的二进制矩阵 grid 。

岛屿 是由一些相邻的 1 (代表土地) 构成的组合，这里的「相邻」要求两个 1 必须在 水平或者竖直的四个方向上 相邻。你可以假设 grid 的四个边缘都被 0（代表水）包围着。

岛屿的面积是岛上值为 1 的单元格的数目。

计算并返回 grid 中最大的岛屿面积。如果没有岛屿，则返回面积为 0 。

https://leetcode.cn/problems/max-area-of-island/

【示例】

【代码】admiin

package com.company;
import java.util.*;

// 2023-04-23
class Solution {
    public int maxAreaOfIsland(int[][] grid) {
        if (grid == null || grid.length == 0) return 0;
        int m = grid.length;
        int n = grid[0].length;
        int res = 0;

        for (int i = 0; i < m; i++){
            for (int j = 0; j < n; j++){
                if (grid[i][j] == 1){
                    res = Math.max(dfs(grid, i, j), res);
                }
            }
        }
        System.out.println(res);
        return res;
    }

    private int dfs(int[][] grid, int i, int j) {
        if (i < 0 || j < 0 || i >= grid.length || j >= grid[i].length || grid[i][j] == 0) return 0;

        int sum = 1;
        grid[i][j] = 0;

        sum += dfs(grid, i + 1, j);
        sum += dfs(grid, i - 1, j);
        sum += dfs(grid, i, j + 1);
        sum += dfs(grid, i, j - 1);
        return sum;
    }

}

public class Test {
    public static void main(String[] args) {
        new Solution().maxAreaOfIsland(new int[][]{{0,0,1,0,0,0,0,1,0,0,0,0,0},{0,0,0,0,0,0,0,1,1,1,0,0,0},
                {0,1,1,0,1,0,0,0,0,0,0,0,0},{0,1,0,0,1,1,0,0,1,0,1,0,0},{0,1,0,0,1,1,0,0,1,1,1,0,0},
                {0,0,0,0,0,0,0,0,0,0,1,0,0},{0,0,0,0,0,0,0,1,1,1,0,0,0},{0,0,0,0,0,0,0,1,1,0,0,0,0}}); // 输出: 6

        new Solution().maxAreaOfIsland(new int[][]{{0,0,0,0,0,0,0,0}}); // 输出: 0
    }
}