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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0601_0700.s0695_max_area_of_island;

// #Medium #Array #Depth_First_Search #Breadth_First_Search #Matrix #Union_Find
// #Algorithm_I_Day_7_Breadth_First_Search_Depth_First_Search
// #Graph_Theory_I_Day_2_Matrix_Related_Problems
// #2022_03_22_Time_3_ms_(76.79%)_Space_47.1_MB_(55.25%)

/**
 * 695 - Max Area of Island\.
 *
 * Medium
 *
 * You are given an `m x n` binary matrix `grid`. An island is a group of `1`'s (representing land) connected **4-directionally** (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.
 *
 * The **area** of an island is the number of cells with a value `1` in the island.
 *
 * Return _the maximum **area** of an island in_ `grid`. If there is no island, return `0`.
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/05/01/maxarea1-grid.jpg)
 *
 * **Input:** grid = \[\[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]]
 *
 * **Output:** 6
 *
 * **Explanation:** The answer is not 11, because the island must be connected 4-directionally. 
 *
 * **Example 2:**
 *
 * **Input:** grid = \[\[0,0,0,0,0,0,0,0]]
 *
 * **Output:** 0 
 *
 * **Constraints:**
 *
 * *   `m == grid.length`
 * *   `n == grid[i].length`
 * *   `1 <= m, n <= 50`
 * *   `grid[i][j]` is either `0` or `1`.
**/
public 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 max = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == 1) {
                    int area = dfs(grid, i, j, m, n, 0);
                    max = Math.max(area, max);
                }
            }
        }
        return max;
    }

    private int dfs(int[][] grid, int i, int j, int m, int n, int area) {
        if (i < 0 || i >= m || j < 0 || j >= n || grid[i][j] == 0) {
            return area;
        }
        grid[i][j] = 0;
        area++;
        area = dfs(grid, i + 1, j, m, n, area);
        area = dfs(grid, i, j + 1, m, n, area);
        area = dfs(grid, i - 1, j, m, n, area);
        area = dfs(grid, i, j - 1, m, n, area);
        return area;
    }
}