0695-max-area-of-island.cpp

/*
    Given grid where '1' is land & '0' is water, return largest island

    DFS, set visited land to '0' to not visit it again, store biggest

    Time: O(m x n)
    Space: O(m x n)
*/

class Solution {
public:
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int m = grid.size();
        int n = grid[0].size();
        
        int result = 0;
        
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == 1) {
                    result = max(result, dfs(grid, i, j, m, n));
                }
            }
        }
        
        return result;
    }
private:
    int dfs(vector<vector<int>>& grid, int i, int j, int m, int n) {
        if (i < 0 || i >= m || j < 0 || j >= n || grid[i][j] == 0) {
            return 0;
        }
        grid[i][j] = 0;
        
        return 1 + dfs(grid, i - 1, j, m, n) + dfs(grid, i + 1, j, m, n)
            + dfs(grid, i, j - 1, m, n) + dfs(grid, i, j + 1, m, n);
    }
};