有n个人围成一圈，顺序排号。从第一个人开始报数（从1到3报数），凡报到3的人退出圈子，问最后留下的是原来第几号的那位。这个程序的中间while循环部分我不是看得很懂？



#include <iostream>
using namespace std;

void main()
{
    int num;
    cout<<"请输入人数"<<endl;
    cin>>num;
    int *pPeople = new int[num];
    for(int i = 0;i<num;i++)
    {
        pPeople[i] = i + 1;
    }
    int count = num;
    int index = 0;
    int k = 1;
    while(count>1)
    {
        if (pPeople[index] != 0)
        {
            if (k==3)
            {
                pPeople[index] = 0;
                count --;
                k = 1;

            }
            else
            {
                k++;
            }
            
        }
        index ++;
        index %= num;
    }
    for(int i=0;i<num;i++)
    {
        if (pPeople[i] != 0)
        {
            cout<<"剩下的这个人的编号是："<<
                pPeople[i]<<endl;
        }
    }
  delete []pPeople;
}