Leetcode 1020. Number of Enclaves

Posted 2021-02-17 周洋的Blog

dfs或者bfs

class Solution:
    def dfs(self, A, rows, cols, i, j):
        if not (0 <= i < rows and 0 <= j < cols):
            return
        elif A[i][j] == 0:
            return
        else:
            A[i][j] = 0
            self.dfs(A, rows, cols, i + 1, j)
            self.dfs(A, rows, cols, i - 1, j)
            self.dfs(A, rows, cols, i, j + 1)
            self.dfs(A, rows, cols, i, j - 1)

    def numEnclaves(self, A: List[List[int]]) -> int:
        rows = len(A)
        cols = len(A[0])
        for j in range(0, cols):
            if A[0][j] == 1:
                self.dfs(A, rows, cols, 0, j)
            if A[rows - 1][j] == 1:
                self.dfs(A, rows, cols, rows - 1, j)

        for i in range(0, rows):
            if A[i][0] == 1:
                self.dfs(A, rows, cols, i, 0)
            if A[i][cols - 1] == 1:
                self.dfs(A, rows, cols, i, cols - 1)

        ans = 0
        for row in A:
            for a in row:
                if a == 1:
                    ans += 1
        return ans

或者

import queue
class Solution:
    def bfs(self, A, rows, cols, i, j):
        q = queue.Queue()
        A[i][j] = 0
        q.put((i, j))
        while not q.empty():
            p = q.get()
            if 0 <= p[0] + 1 < rows and A[p[0] + 1][p[1]] == 1:
                A[p[0] + 1][p[1]] = 0
                q.put((p[0] + 1, p[1]))
            if 0 <= p[0] - 1 < rows and A[p[0] - 1][p[1]] == 1:
                A[p[0] - 1][p[1]] = 0
                q.put((p[0] - 1, p[1]))
            if 0 <= p[1] + 1 < cols and A[p[0]][p[1] + 1] == 1:
                A[p[0]][p[1] + 1] = 0
                q.put((p[0], p[1] + 1))
            if 0 <= p[1] - 1 < cols and A[p[0]][p[1] - 1] == 1:
                A[p[0]][p[1] - 1] = 0
                q.put((p[0], p[1] - 1))

    def numEnclaves(self, A: List[List[int]]) -> int:
        rows = len(A)
        cols = len(A[0])
        for j in range(0, cols):
            if A[0][j] == 1:
                self.bfs(A, rows, cols, 0, j)
            if A[rows - 1][j] == 1:
                self.bfs(A, rows, cols, rows - 1, j)

        for i in range(0, rows):
            if A[i][0] == 1:
                self.bfs(A, rows, cols, i, 0)
            if A[i][cols - 1] == 1:
                self.bfs(A, rows, cols, i, cols - 1)

        ans = 0
        for row in A:
            for a in row:
                if a == 1:
                    ans += 1
        return ans