n-queens（n皇后问题）

n queens ii（n皇后问题-只计数不保存）

问题描述

The n queens puzzle is the problem of placing n queens on an N x Nchessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle.
Each solution contains a distinct board configuration of the n-queens’ placement, where’Q’and’.'both indicate a queen and an empty space respectively.
For example,
There exist two distinct solutions to the 4-queens puzzle:

题目大意

著名n皇后问题。
n个皇后摆放在N x N的棋盘格中，使得横、竖和两个对角线方向均不会同时