N皇后

#include<bits/stdc++.h>
using namespace std;

int n;
int a[15];
bool v[15];

bool eaten(int x1, int y1){
    for(int i = 1; i <= n; i++){
        if(v[i]){
            if(y1 == a[i] || x1 - i == y1 - a[i] || x1 + y1 == i + a[i]){
                return true;
            }
        }
    }
    return false;
}

void dfs(int x){
    if(x == n + 1){
        for(int i = 1; i <= n; i++){
            for(int j = 1; j <= n; j++){
                if(a[i] == j) cout << 'Q';
                else cout << '.';
            }
            cout << endl;
        }
        cout << endl;
        return;
    }
    for(int i = 1; i <= n; i++){
        if(!eaten(x, i)){
            a[x] = i;
            v[x] = true;
            dfs(x + 1);
            v[x] = false;
        }
    }
}

int main(){
    cin >> n;
    dfs(1);
    return 0;
}