• Time:O(mn)
• Space:O(1)

## C++

``````class Solution {
public:
int maxAreaOfIsland(vector<vector<int>>& grid) {
int ans = 0;

for (int i = 0; i < grid.size(); ++i)
for (int j = 0; j < grid[0].size(); ++j)
ans = max(ans, dfs(grid, i, j));

return ans;
}

private:
int dfs(vector<vector<int>>& grid, int i, int j) {
if (i < 0 || i == grid.size() || j < 0 || j == grid[0].size())
return 0;
if (grid[i][j] != 1)
return 0;

grid[i][j] = 2;

return 1 + dfs(grid, i + 1, j) + dfs(grid, i - 1, j)
+ dfs(grid, i, j + 1) + dfs(grid, i, j - 1);
}
};
``````

## JAVA

``````class Solution {
public int maxAreaOfIsland(int[][] grid) {
int ans = 0;

for (int i = 0; i < grid.length; ++i)
for (int j = 0; j < grid[0].length; ++j)
ans = Math.max(ans, dfs(grid, i, j));

return ans;
}

private int dfs(int[][] grid, int i, int j) {
if (i < 0 || i == grid.length || j < 0 || j == grid[0].length)
return 0;
if (grid[i][j] != 1)
return 0;

grid[i][j] = 2;

return 1 + dfs(grid, i + 1, j) + dfs(grid, i - 1, j)
+ dfs(grid, i, j + 1) + dfs(grid, i, j - 1);
}
}
``````

## Python

``````class Solution:
def maxAreaOfIsland(self, grid: List[List[int]]) -> int:
def dfs(i: int, j: int) -> int:
if i < 0 or i == len(grid) or j < 0 or j == len(grid[0]):
return 0
if grid[i][j] != 1:
return 0

grid[i][j] = 2

return 1 + dfs(i + 1, j) + dfs(i - 1, j) + dfs(i, j + 1) + dfs(i, j - 1)

return max(dfs(i, j) for i in range(len(grid)) for j in range(len(grid[0])))
``````