12. 8-QUEENS.CPP

#include<stdio.h>
#include<stdlib.h>
#include<iostream>
#include<math.h>
#define R 50
using namespace std;

int x[R], count;

int place(int k,int i)
{
	int j;
	for(j=1;j<k;j++)
	{
		if( x[j]==i || abs(x[j]-i)==abs(j-k) )
			return 0;
	}
	return 1;
}
void NQueens(int k,int n)
{
	int i,j;
	for(i=1;i<=n;i++)
	{
		if(place(k,i)==1)
		{
			x[k]=i;
			if(k==n)
			{
				count++;
				cout<<"Solution "<<count<<".\n";
				cout<<" Row:Column = ";
				for(j=1;j<=n;j++)
					cout<<j<<":"<<x[j]<<" ";
				cout<<endl;
			}
			else NQueens(k+1,n);
		}
	}
}

int main()
{
	int n;

	cout<<"  *** 8-Queens Chess Problem ***\n";
	do
	{	cout<<"\nEnter number of Queens(0 to quit) : ";
		cin>>n;

		count=0;
		NQueens(1,n);
	}while(n);
	return 0;
}