N-Queens N皇后问题 DFS

The n-queens puzzle is the problem of placing n queens on an n×n chessboard 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:

[
 [".Q..",  // Solution 1
  "...Q",
  "Q...",
  "..Q."],

 ["..Q.",  // Solution 2
  "Q...",
  "...Q",
  ".Q.."]
]

N皇后问题，DFS。

/*2015.8.18cyq*/
#include 
#include 
#include 
using namespace std;

class Solution {
public:
    vector> solveNQueens(int n) {
		vector board(n,string(n,'-'));//'-'表示未放置,'.'表示禁止放置
		vector> result;
		dfs(board,0,n,result);
		return result;
    }
private:
	void dfs(vector &board,int row,int n,vector> &result){
		if(row==n){
			result.push_back(board);
			return ;
		}
		for(int col=0;col tmp(board);//创建副本再修改局势，避免board的恢复
				for(int i=0;i > result=solu.solveNQueens(4);
	cout<