0827.py

class Solution:
    def largestIsland(self, grid):
        r, c = len(grid), len(grid[0])
        
        def check(x, y):
            if x < 0 or x >= r or y < 0 or y >= c:
                return 0
            return 1
        
        def dfs(x, y, color):
            if not check(x, y) or grid[x][y] != 1:
                return 0
            res = 1
            grid[x][y] = color
            for i, j in [[1, 0], [-1, 0], [0, 1], [0, -1]]:
                res += dfs(x + i, y + j, color)
            return res
        
        data, res, color = [0, 0], 0, 2
        for i in range(r):
            for j in range(c):
                if grid[i][j] == 1:
                    data.append(dfs(i, j, color))
                    color += 1

        for i in range(r):
            for j in range(c):
                if grid[i][j] == 0:
                    colors = set(grid[x+i][y+j] for x, y in [[1, 0], [-1, 0], [0, 1], [0, -1]] if check(i + x, j + y))
                    res = max(res, sum(data[color] for color in colors) + 1)
        return r*c if res == 0 else res