C - Programming Guide

 #include<stdio.h>
#include<iostream.h>
#include<conio.h>
#include<math.h>
#include<time.h>

class queen
{
  public:
        int x[20],count;
        void nqueen(int,int);
        int place(int,int);
        void write(int x[],int);
};

int main()
{
  int i,n;
  char k='y';
  queen q;
  do
  {
    clrscr();
    float toc;
    clock_t end,start;
    start=clock();
    cout<<"\n\t\t\t N-Queens Problem";
    cout<<"\n\t\t\t------------------";
    cout<<"\n\n\t\tEnter Size of Chessboard :: ";
    cin>>n;
    q.count=0;
    q.nqueen(1,n);
    cout<<"\n\t\tTotal No of Solutions ::"<<q.count;
    end=clock();
    toc=(end - start)/CLK_TCK;
    cout<<"\n\t\tTime Complexity :: "<<toc;
    cout<<"\n\t\tDo you want to continue?(y/n)";
    k=getche();
  }while(k=='y');
  return 0;
}

void queen::nqueen(int k,int n)
{
  int i;
  for(i=1;i<=n;i++)
  {
    if(place(k,i))
    {
        x[k]=i;
        if(k==n)
            write(x,n);
        else
            nqueen(k+1,n);
    }
  }
}

int queen::place(int k,int i)
{
  int j;
  for(j=1;j<=k-1;j++)
  {
    if((x[j]==i) || (abs(x[j]-i) == abs(j-k)))
        return 0;
  }
  return 1;
}

void queen::write(int x[],int n)
{
  int i,j;
  cout<<"\n\n\t\t"<<count+1<<") Possible Solution :: ";
  for(i=1;i<=n;i++)
  {
    cout<<" "<<x[i];
  }
  cout<<"\n";
  for(i=1;i<=n;i++)
  {
    cout<<"\n\t\t\t";
    for(j=1;j<=n;j++)
    {

    if(j==x[i])
        cout<<"  Q ";
    else
        cout<<"  x ";
    }

  }
  cout<<"\n\n";
  count++;
}