八皇后

#include <fstream>
#include <cmath>
#define MAX 8
using namespace std;

ofstream cout("out");

int queens[MAX];
int sum=0;

void print();
void placequeens(int i);
bool isValid(int n);

void print(){
    for (int i=0;i<MAX;i++){
        for (int j=0;j<MAX;j++){
            if(j==queens[i])
                cout<<"Q ";
            else 
                cout<<". ";
        }
        cout<<endl;
    }
}

void placequeens(int i){
    for (int j=0;j<MAX;j++){
        if(i==MAX){
            sum++;
            cout<<"# "<<sum<<endl;
            print();
            return;
        }
        queens[i]=j;
        if(isValid(i))    placequeens(i+1);
    }
}

bool isValid(int n){
    for (int i=0;i<n;i++){
        if(queens[i]==queens[n])    return false;
        if(abs(queens[i]-queens[n])==(n-i))    return false;
    }
    return true;
}

int main() 
{
    placequeens(0);
    cout<<"total "<<sum<<"."<<endl;
    return 0;
}