diff --git a/python/number_of_enclaves.py b/python/number_of_enclaves.py new file mode 100644 index 0000000..73f6248 --- /dev/null +++ b/python/number_of_enclaves.py @@ -0,0 +1,42 @@ +# https://leetcode.com/problems/number-of-enclaves/description/ +# T: O(m*n) +# S: O(m*n) + +from typing import List + +class Solution: + def dfs(self, x: int, y: int, m: int, n: int, grid: List[List[int]], visit: List[List[bool]]): + if x < 0 or x >= m or y < 0 or y >= n or visit[x][y] or grid[x][y] == 0: + return + visit[x][y] = True + self.dfs(x+1, y, m, n, grid, visit) + self.dfs(x-1, y, m, n, grid, visit) + self.dfs(x, y+1, m, n, grid, visit) + self.dfs(x, y-1, m, n, grid, visit) + + def numEnclaves(self, grid: List[List[int]]) -> int: + m, n = len(grid), len(grid[0]) + visit = [[False for _ in range(n)] for _ in range(m)] + + # Traverse the first and last columns. + for i in range(m): + if grid[i][0] == 1 and not visit[i][0]: + self.dfs(i, 0, m, n, grid, visit) + if grid[i][n-1] == 1 and not visit[i][n-1]: + self.dfs(i, n-1, m, n, grid, visit) + + # Traverse the first and last rows. + for j in range(n): + if grid[0][j] == 1 and not visit[0][j]: + self.dfs(0, j, m, n, grid, visit) + if grid[m-1][j] == 1 and not visit[m-1][j]: + self.dfs(m-1, j, m, n, grid, visit) + + # Count the number of unvisited land cells. + count = 0 + for i in range(m): + for j in range(n): + if grid[i][j] == 1 and not visit[i][j]: + count += 1 + + return count