C ++和python在AugustQueens上的结果不同

Question

I encountered a problem in solving the eight queen problems. I first wrote the following code in C++.

#include <iostream>
#include <cmath>
using namespace std;
bool flag=true;
void queen(int *arr,int n,int cnt){
    if(cnt==n){
        for(int i=0;i<n;i++){
            cout<<arr[i]<<" ";
        }
        return;
    }
    for(int col=0;col<n;col++){
        arr[cnt]=col;
         flag=true;
         for(int row=0;row<cnt;row++){
             if(arr[row]==col||(abs(col-arr[row])==cnt-row)){
                 flag=false;
                 break;
             }
         }
         if(flag){
             cnt++;
             queen(arr,n,cnt);
         }
    }
}

int main() {
    int n=8;
    int arr[n]={0};
    queen(arr,n,0);
}

This should get correct results,but nothing is output.So I wrote the simpler code in python with the same idea as follows.

count=0
def queen(A, cnt=0):
    global count
    if cnt == len(A):
        print(A)
        count+=1
        return 0
    for col in range(len(A)):
        A[cnt], flag = col, True
        for row in range(cnt):
            if A[row] == col or abs(col - A[row]) == cnt - row:
                flag = False
                break
        if flag:
            queen(A, cnt+1)
queen([None]*8)
print(count)

This time I got the correct answer. I don't think any difference between these two codes. I was wondering someone could point out what's wrong with the c++ codes.

[0, 4, 7, 5, 2, 6, 1, 3]
[0, 5, 7, 2, 6, 3, 1, 4]
[0, 6, 3, 5, 7, 1, 4, 2]
[0, 6, 4, 7, 1, 3, 5, 2]
[1, 3, 5, 7, 2, 0, 6, 4]
......
[7, 1, 4, 2, 0, 6, 3, 5]
[7, 2, 0, 5, 1, 4, 6, 3]
[7, 3, 0, 2, 5, 1, 6, 4]
92

Answer 1

I think this is the problem:

     if(flag){
         cnt++;
         queen(arr,n,cnt);
     }

When you return cnt , is still incremented. You want:

         queen(arr, n, cnt + 1);

which matches what happens in your Python version.