• 关键在y=x+b 和 y= -x+b 来确定主对角线和副角线

#include<iostream>
using namespace std;
const int MAXN = 10;
int map[MAXN][MAXN];
bool col[MAXN],dg[MAXN*2],udg[MAXN*2];
int n;
void print(){
    for(int i = 1;i<=n;i++){
        for(int j = 1;j<=n;j++){
            map[i][j]? cout<<"Q":cout<<".";
        }
        cout<<endl;
    }
}
void dfs(int step){
    if(step == n+1){
        print();
        cout<<endl;
    }else{
        for(int i = 1;i<=n;i++){
            if(col[i] == 0 && dg[step-i+n] == 0 && udg[step+i]==0){
                col[i] = dg[step-i+n] = udg[step+i] = 1;
                map[step][i] = 1;
                dfs(step+1);
                map[step][i] = 0;
                col[i] = dg[step-i+n] = udg[step+i] = 0;
            }
        }
    }

}
int main(){
    cin>>n;
    for(int i = 0;i<=n;i++){
        for(int j = 0;j<=n;j++){
            map[i][j] = 0;
        }
    }
    dfs(1);
}