51. N-Queens

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.."]
]

/* ***********************************************
Author        :guanjun
Created Time  :2016/4/3 12:48:50
File Name     :1.cpp
************************************************ */
#include <iostream>
#include <cstring>
#include <cstdlib>
#include <stdio.h>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <iomanip>
#include <list>
#include <deque>
#include <stack>
#define ull unsigned long long
#define ll long long
#define mod 90001
#define INF 0x3f3f3f3f
#define maxn 10010
#define cle(a) memset(a,0,sizeof(a))
const ull inf = 1LL << 61;
const double eps=1e-5;
using namespace std;
priority_queue<int,vector<int>,greater<int> >pq;
struct Node{
    int x,y;
};
struct cmp{
    bool operator()(Node a,Node b){
        if(a.x==b.x) return a.y> b.y;
        return a.x>b.x;
    }
};
class Solution {
public:
    void dfs(int n,int cur,vector<string>&v,vector<vector<string>>&u,int *row,int *col,int *zu,int *fu){
        if(cur==n){
            u.push_back(v);
            return ;
        }
        for(int j=0;j<n;j++){
            if(v[cur][j]=='.'&&(row[cur]==0)&&(col[j]==0)&&(zu[j-cur+n]==0)&&(fu[j+cur]==0)){
                v[cur][j]='Q';
                row[cur]=col[j]=zu[j-cur+n]=fu[j+cur]=1;
                dfs(n,cur+1,v,u,row,col,zu,fu);
                 row[cur]=col[j]=zu[j-cur+n]=fu[j+cur]=0;
                v[cur][j]='.';
            }
        }
        //  dfs(cur+1)
    }
    vector<vector<string>> solveNQueens(int n) {
        vector<string>v;
        vector<vector<string>>u;
        int zu[100]={0};
        int fu[100]={0};
        int col[100]={0};
        int row[100]={0};
        
        for(int i=0;i<n;i++){
            string s="";
            for(int j=0;j<n;j++)
                s+=".";
            v.push_back(s);
        }
        dfs(n,0,v,u,row,col,zu,fu);
        return u;
    }
};
bool cmp(int a,int b){
    return a>b;
}
int main()
{
    #ifndef ONLINE_JUDGE
    //freopen("in.txt","r",stdin);
    #endif
    //freopen("out.txt","w",stdout);
    Solution a;
    vector<vector<string>>u=a.solveNQueens(4);
    for(int i=0;i<u.size();i++){
        for(int j=0;j<4;j++){
            cout<<u[i][j]<<endl;
        }
    }
    return 0;
}