2023.04.06 Today's Challenge

https://leetcode.com/problems/number-of-closed-islands/

Number of Closed Islands - LeetCode

DFS의 전형적인 문제

class Solution:
    def closedIsland(self, grid: List[List[int]]) -> int:
        rs, cs = len(grid), len(grid[0])
        cnt = 0

        def dfs(i, j):
            if i < 0 or j < 0 or i >= rs or j >= cs:
                return False
            if grid[i][j] == 1:
                return True
            grid[i][j] = 1
            left = dfs(i, j-1)
            right = dfs(i, j+1)
            up = dfs(i-1, j)
            down = dfs(i+1, j)

            return left and right and up and down

        for i in range(rs):
            for j in range(cs):
                if grid[i][j] == 0 and dfs(i, j):
                    cnt += 1
            
        return cnt