class Solution {
    public int maxAreaOfIsland(int[][] grid) {
        int max = 0;
        if (grid == null || grid.length == 0 || grid[0].length == 0) return max;
        boolean[][] visited = new boolean[grid.length][grid[0].length];
        
        for (int i = 0; i < grid.length; i++) {
            for (int j = 0; j < grid[i].length; j++) {
                if (grid[i][j] == 1 && !visited[i][j]) {
                    max = Math.max(max, dfs(grid, i, j, visited));
                }
            }
        }
        
        return max;
    }
    
    private int dfs(int[][] grid, int i, int j, boolean[][] visited) {
        if (i < 0 || i >= grid.length || j < 0 || j >= grid[i].length || grid[i][j] == 0 || visited[i][j]) return 0;
        
        visited[i][j] = true;
        
        int sum = 1;
        
        sum += dfs(grid, i + 1, j, visited);
        sum += dfs(grid, i - 1, j, visited);
        sum += dfs(grid, i, j + 1, visited);
        sum += dfs(grid, i, j - 1, visited);
        
        return sum;
    }
}