You are given anm x nbinary matrixgrid. An island is a group of1's (representing land) connected4-directionally(horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.

Theareaof an island is the number of cells with a value1in the island.

Returnthe maximumareaof an island in

Example 1:

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 either0or1.

class Solution {
    public int maxAreaOfIsland(int[][] grid) {
        int res = 0;
        for(int i = 0; i < grid.length; i++) {
            for(int j = 0
 
; j < grid[0].length; j++) {
                if(grid[i][j] == 1) {
                    res = Math.max(res, dfs(i, j, grid));
                }
            }
        }
        return res;
    }
    
    public int dfs(int i, int j, int[][] grid) {
        if(i >= grid.length || i < 0 || j < 0 || j >= grid[0].length || grid[i][j] == 0) return 0;

        grid[i][j] = 0;
        return 1 + dfs(i, j - 1, grid)+
        dfs(i-1, j, grid)+
        dfs(i+1, j, grid)+
        dfs(i, j+1, grid);
    }
}

similar to #200.