Leetcode: 695. Max Area of Island && Leetcode 200: Num of Islands

695:

Given a non-empty 2D array gridof 0’s and 1’s, 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.
Find the maximum area of an island in the given 2D array. (If there is no island, the maximum area is 0.)
Example:

[[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]]

Given the above grid, return 6. Note the answer is not 11, because the island must be connected 4-directionally.

Solution:

class Solution {
    public int maxAreaOfIsland(int[][] grid) {
    	int maxArea = 0;
    	for (int i = 0; i < grid.length; i++) {
    		for (int j = 0; j < grid[0].length; j++) {
    			if (grid[i][j] == 1) {
    				maxArea = Math.max(maxArea, findMax(grid, i, j));
    			}
    		}
    	}
    	return maxArea;
    }
    
    private int findMax(int[]grid, int i, int j) {
    	if (grid[i][j] == 1 && i >= 0 && i < grid.length && j >= 0 && j < grid[0].length) {
    		grid[i][j] = 0;
    		return (1 + findMaxArea(grid, i+1, j) + findMaxArea(grid, i-1, j) + findMaxArea(grid, i, j-1) + findMaxArea(grid, i, j+1));
    	}
    	return 0;
    }
}

200:

Given a 2d grid map of '1’s (land) and '0’s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Solution:

class Solution {
    public int numIslands(char[][] grid) {
        if (grid.length == 0 || grid == null) {
            return 0;
        }
        int ans = 0;
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[0].length; j++) {
                if (grid[i][j] == '1') {
                    ans++;
                    findIsland(grid, i, j);
                }
            }
        }
        return ans;
    }
    
    private void findIsland(char[][] grid, int i, int j) {
        if (i >= 0 && i < grid.length && j >= 0 && j < grid[0].length && grid[i][j] == '1') {
            grid[i][j] = '0';
            findIsland(grid, i+1, j);
            findIsland(grid, i-1, j);
            findIsland(grid, i, j+1);
            findIsland(grid, i, j-1);
        }
        return;
    }
 }