菜鸟的每日力扣系列——1020. 飞地的数量（#Day35）

from typing import List


def numEnclaves(grid: List[List[int]]) -> int:
    m, n = len(grid), len(grid[0])
    res = 0

    def dfs(x: int, y: int):
        grid[x][y] = 0  # 将经过的岛屿标记为0
        for nx, ny in ((x-1, y), (x+1, y), (x, y-1), (x, y+1)):  # 上下左右四个前进方向
            if 0 <= nx < m and 0 <= ny < n and grid[nx][ny] == 1:
                dfs(nx, ny)
    # 从网格边界四条边开始
    for j in range(n):
        if grid[0][j] == 1:  # 第一行
            dfs(0, j)
        if grid[m-1][j] == 1:  # 最后一行
            dfs(m-1, j)
    for i in range(m):
        if grid[i][0] == 1:  # 第一列
            dfs(i, 0)
        if grid[i][n-1] == 1:  # 最后一列
            dfs(i, n-1)
    # 统计整个grid剩下的1的个数
    for i in range(m):
        for j in range(n):
            if grid[i][j] == 1:
                res += 1
    return res


grid = [[0, 0, 0, 0], [1, 0, 1, 0], [0, 1, 1, 0], [0, 0, 0, 0]]
print(numEnclaves(grid))  # 3