C ++ implements the n queen problem

// Reference books: Computer Algorithm basics-the third edition of Huazhong University of Science and Technology

// Use the backtracking method to implement the n queen problem. The nqueens (int K) method is implemented recursively. To improve efficiency, it can be changed to non-recursion.

//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 resultpublic: 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!\n"; return 0;}