695. Max Area of Island

This is like number of islands except we also have to count the size of each island, which is done like so.

class Solution:
    def maxAreaOfIsland(self, grid: List[List[int]]) -> int:
        max_area = 0
        visited = set()
        m, n = len(grid), len(grid[0])
 
        def inbounds(y, x):
            return 0 <= y < m and 0 <= x < n
        
        def visit(y, x):
            if (y, x) in visited:
                return 0
            if not inbounds(y, x):
                return 0
            if grid[y][x] != 1:
                return 0
            visited.add((y, x))
            dirs = [(0, 1), (1, 0), (0, -1), (-1, 0)]
            return 1 + sum([visit(dy + y, dx + x) for dy, dx in dirs])
            
        for y in range(m):
            for x in range(n):
                if grid[y][x] == 1:
                    max_area = max(max_area, visit(y, x))
        
        return max_area