LeetCode题解(0526)：优美的排列(Python)

题目：​​原题链接​​（中等）

标签：回溯算法、递归

解法	时间复杂度	空间复杂度	执行用时
Ans 1 (Python)	O ( N ! )	O ( N )	1804ms (20.71%)
Ans 2 (Python)
Ans 3 (Python)

解法一：

class Solution:
    def __init__(self):
        self.N = 0
        self.ans = 0
        self.now = []

    def countArrangement(self, N: int) -> int:
        self.N = N
        self.now = [0] * (N + 1)
        self.dfs(1)
        return self.ans

    def dfs(self, i):
        if i == self.N + 1:
            self.ans += 1
        for j in range(1, self.N + 1):
            if self.now[j] == 0 and (i % j == 0 or j % i == 0):
                self.now[j] = i
                self.dfs(i + 1)
                self.now[j] = 0