Max Area of Island

Published at25 Jul 2026

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You are given a 2D grid containing '1' (land) and '0' (water). Find the maximum area of an island. An island is formed by connecting adjacent land cells horizontally or vertically.

Use DFS to explore each island. When a '1' is found, compute its area via DFS by counting all connected land cells, then mark them as visited. Track the maximum area found.

Time is O(m*n) and space is O(m*n) for the recursion stack.

Example Input & Output

Example 1

Input

[["0"]]

Output

Explanation

No land

Example 2

Input

[["1"]]

Output

Explanation

Single cell

Example 3

Input

[["1","1"],["1","1"]]

Output

Explanation

2x2 island

Example 4

Input

[["0","0","0"],["0","0","0"]]

Output

Explanation

No land

Example 5

Input

[["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

Explanation

Max area is 6 (the island in top-right)

Algorithm Flow

Recommendation Algorithm Flow for Max Area of Island

Solution Approach

function solution(grid) {
  var rows = grid.length, cols = grid[0].length, maxArea = 0;
  function dfs(i, j) {
    if (i < 0 || i >= rows || j < 0 || j >= cols || grid[i][j] === '0') return 0;
    grid[i][j] = '0';
    return 1 + dfs(i-1,j) + dfs(i+1,j) + dfs(i,j-1) + dfs(i,j+1);
  }
  for (var i = 0; i < rows; i++) {
    for (var j = 0; j < cols; j++) {
      if (grid[i][j] === '1') { var area = dfs(i, j); if (area > maxArea) maxArea = area; }
    }
  }
  return maxArea;
}

Best Answers
These are the verified best solutions for this Challenge. You can use them as a reference to improve your solution.

java

class Solution {
    int r,c;
    public int solution(String[][] g) {
        if(g==null||g.length==0)return 0;r=g.length;c=g[0].length;int mx=0;
        for(int i=0;i<r;i++)for(int j=0;j<c;j++)if(g[i][j].equals("1"))mx=Math.max(mx,dfs(g,i,j));
        return mx;
    }
    int dfs(String[][] g,int i,int j){
        if(i<0||i>=r||j<0||j>=c||g[i][j].equals("0"))return 0;
        g[i][j]="0";return 1+dfs(g,i-1,j)+dfs(g,i+1,j)+dfs(g,i,j-1)+dfs(g,i,j+1);
    }
}

javascript

function solution(g){var r=g.length,c=g[0].length,mx=0;function dfs(i,j){if(i<0||i>=r||j<0||j>=c||g[i][j]==='0')return 0;g[i][j]='0';return 1+dfs(i-1,j)+dfs(i+1,j)+dfs(i,j-1)+dfs(i,j+1);}for(var i=0;i<r;i++){for(var j=0;j<c;j++){if(g[i][j]==='1')mx=Math.max(mx,dfs(i,j));}}return mx;}

php

<?php
function solution($g){$r=count($g);$c=count($g[0]);$mx=0;
    $dfs=function(&$g,$i,$j)use(&$dfs,$r,$c){
        if($i<0||$i>=$r||$j<0||$j>=$c||$g[$i][$j]==='0')return 0;
        $g[$i][$j]='0';return 1+$dfs($g,$i-1,$j)+$dfs($g,$i+1,$j)+$dfs($g,$i,$j-1)+$dfs($g,$i,$j+1);
    };
    for($i=0;$i<$r;$i++)for($j=0;$j<$c;$j++)if($g[$i][$j]==='1')$mx=max($mx,$dfs($g,$i,$j));
    return $mx;
}

python

def solution(grid):
    if not grid or not grid[0]: return 0
    r,c=len(grid),len(grid[0])
    def dfs(i,j):
        if i<0 or i>=r or j<0 or j>=c or grid[i][j]=='0':return 0
        grid[i][j]='0'
        return 1+dfs(i-1,j)+dfs(i+1,j)+dfs(i,j-1)+dfs(i,j+1)
    mx=0
    for i in range(r):
        for j in range(c):
            if grid[i][j]=='1':mx=max(mx,dfs(i,j))
    return mx

rust

fn solution(mut g:Vec<Vec<String>>)->i32{let r=g.len();if r==0{return 0;}let c=g[0].len();let mut mx=0;for i in 0..r{for j in 0..c{if g[i][j]=="1"{mx=mx.max(dfs(&mut g,i as i32,j as i32,r as i32,c as i32));}}}mx}
fn dfs(g:&mut Vec<Vec<String>>,i:i32,j:i32,r:i32,c:i32)->i32{if i<0||i>=r||j<0||j>=c||g[i as usize][j as usize]=="0"{return 0;}g[i as usize][j as usize]="0".to_string();1+dfs(g,i-1,j,r,c)+dfs(g,i+1,j,r,c)+dfs(g,i,j-1,r,c)+dfs(g,i,j+1,r,c)}

typescript

function solution(g:string[][]):number{var r=g.length,c=g[0].length,mx=0;function dfs(i:number,j:number):number{if(i<0||i>=r||j<0||j>=c||g[i][j]==='0')return 0;g[i][j]='0';return 1+dfs(i-1,j)+dfs(i+1,j)+dfs(i,j-1)+dfs(i,j+1);}for(var i=0;i<r;i++){for(var j=0;j<c;j++){if(g[i][j]==='1')mx=Math.max(mx,dfs(i,j));}}return mx;}

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Max Area of Island

Example Input & Output

Algorithm Flow

Solution Approach

Best AnswersThese are the verified best solutions for this Challenge. You can use them as a reference to improve your solution.

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Best Answers
These are the verified best solutions for this Challenge. You can use them as a reference to improve your solution.