杂谈：经典算法之八皇后问题

class Solution:
    def totalNQueens(self, n: int) -> int:
        ans = 0
        cache = []
        
        def dfs(i):
            nonlocal ans, cache
            if i >= n:
                ans += 1
                return
            for j in range(n):
                if any(c == j or i-r == abs(c-j) for r, c in cache):
                    continue
                cache.append((i, j))
                dfs(i+1)
                cache.pop()
            return
        
        dfs(0)
        return ans