8.1 Problem D: [Introduction to Recursion] n Queens Problem (original 8 Queens Problem)

Title description

       Those who can play chess know very well: the queen can take any other pieces on the horizontal, vertical, and diagonal lines without a limit. How to put 8 queens on the board (there are 8 * 8 squares) so that none of them can be eaten! This is the famous Eight Queens problem.

 

enter

An integer n (1 <= n <= 10) 

Output

Each line of output corresponds to a scheme, and all schemes are output in lexicographic order. Each scheme outputs the column number of the queen in order, separated by a space between two adjacent numbers. If there is no set of feasible solutions, output "no solute!"

Sample input Copy

4

Sample output Copy

2 4 1 3
3 1 4 2

#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
int n,a[20],ans,cnt,b[800][20];
void dfs(int deep)
{
    if(deep==n+1){
        ans++;
        for(int i=1;i<=n;i++) b[cnt][i]=a[i];
        cnt++;
        return;
    }
    for(int i=1;i<=n;i++){
        bool flag=true;///判断当前位置是否合法
        for(int j=1;j<deep;j++){
            if(a[j]==i||(deep-j)==abs(i-a[j])){
                flag=false;
                break;
            }
        }
        if(flag){//如果当先位置合法，则递归搜索下一个合法位置
            a[deep]=i;
            dfs(deep+1);
        }
    }
    return;
}
int main()
{
    while(scanf("%d",&n)!=EOF){
        cnt=0;
        ans=0;
        dfs(1);
        if(ans==0) printf("no solute!\n");
        else{
            for(int i=0;i<cnt;i++){
                for(int j=1;j<=n;j++){
                    printf("%d ",b[i][j]);
                }
                printf("\n");
            }
        }
    }
    return 0;
}