C++実現n皇后問題

//書籍参照:コンピュータアルゴリズム基礎-華中科技大学第三版
//n皇后問題を遡及法で実現し、nqueens(int k)法を再帰で実現し、効率を高めるために非再帰に変更することができる

//queen.h--Queen class
#ifndef _QUEEN_H_
#define _QUEEN_H_
#include<iostream>
class Queen
{
private:
 int queens;//total queens
 int *answer;//answer array 
 int sum;//total answers
 //judge a certain place is available,k represent row,i represent column
 bool place(int k,int i)const;
 void printResult()const;//print result
public:
 Queen(int n);
 ~Queen();
 void nqueens(int k=1);//search the solutionof vector space under the condition 
 void printSum()const{ std::cout<<sum<<std::endl;}
};
#endif
//N_QUEEN.cpp--Queen class methods
#include<cmath>
#include"queen.h"
Queen::Queen(int n)
{
 queens=n;
 answer=new int[n+1];
 sum=0;
}
Queen::~Queen()
{
 delete []answer; 
}

void Queen::nqueens(int k)
{
 answer[k]=1;
 while(answer[k]<=queens)
 {
  if(place(k,answer[k]))
  {
   if(k==queens)
   {
    sum++;
    printResult();
   }
   else
    nqueens(k+1);
  }
   answer[k]=answer[k]+1;
 }
}
bool Queen::place(int k,int i)const
{
 int m=1;
 while(m<k)
 {
  if(answer[m]==answer[k]||abs(answer[k]-answer[m])==abs(k-m))
   return false;
  m++;
 }
 return true;
}
void Queen::printResult()const
{
 for(int i=1;i<queens;i++)
 {
     std::cout<<answer[i]<<"  ";
 }
 std::cout<<std::endl;
}
//use.cpp--test Queen class
#include<iostream>
#include"queen.h"
int main()
{
 std::cout<<"Enter the queens:";
 int m;
 std::cin>>m;
 Queen q=Queen(m);
 q.nqueens();
 std::cout<<"Total methods: ";
 q.printSum();
 std::cout<<"Done!
";
 return 0;
}