指针对象，无法突破输入循环

Question

我的程序从用户读取输入并设置目标，然后从用户读取更多输入。然后，它会比较目标初始化后输入的数字和执行次数greater_than，less_than和equal。我很困惑为什么当我输入＆＃39; ctrl + d＆＃39;时我的程序不会突破循环。命令不再输入。这是我的期中考试题的代表性例子所以我不允许改变main（）;或者在list.h中，我并没有违反我的任何教师作弊政策，因为我没有参与这项工作，而是使用了作为学习方法的解决方案。

这是我的代码，提前谢谢。

的main.cpp

#include <iostream>
using namespace std;
#include "list.h"

int main()
{
    List list;
    int value;
    int target;

    // first number read is the target
    cin >> target;

    while (cin >> value)
    {
      list.insert(value);
    }

    // initialized to 100 to make sure List::compare() initializes them correctly
    int less_than = 100;
    int equal = 100;
    int greater_than = 100;
    list.compare(target, less_than, equal, greater_than);

    cout << "target = " << target << endl;
    cout << "less_than = " << less_than << endl;
    cout << "equal = " << equal << endl;
    cout << "greater_than = " << greater_than << endl;
}

list.h

//链接整数列表

#ifndef LIST_H
#define LIST_H

class List
{
    public:
        List();
        ~List();
        void insert(int value); // insert at beginning of list
        void print(); // print all values in the list
        void compare(int target, int &less_than, int &equal, int &greater_than);

    private:
        class Node
        {
            public:
                Node(int value, Node *next)
                {m_value = value; m_next = next;}
                int m_value;
                Node *m_next;
        };
        Node *m_front;
};

#endif

list.cpp

#include <iostream>
using namespace std;
#include "list.h"

List::List()
{
    m_front = NULL;
}

// delete all Nodes in the list
// since they are dynamically allocated using new, they won't go away
// automatically when the list is deleted
// Rule of thumb: destructor deletes all memory created by member functions
List::~List()
{
    while (m_front)
    {
        Node *tmp = m_front;
        m_front = m_front->m_next;
        delete tmp;
    }
}

// always insert at the front of the list
// Note: this works even in the SPECIAL CASE that the list is empty
void List::insert(int value)
{
    m_front = new Node(value, m_front);
}

// iterate through all the Nodes in the list and print each Node
void List::print()
{
    for (Node *ptr = m_front; ptr; ptr = ptr->m_next)
    {
        cout << ptr->m_value << endl; 
    }
}

void List::compare(int target, int &less_than, int &equal, int &greater_than)
{

  less_than = 0;
  equal = 0;
  greater_than = 0;
  int targ;
  targ = target;


  Node *ptr = m_front;
  while(ptr != NULL){

if(ptr ->m_value == targ){

  equal++;
}
else if (ptr -> m_value > targ){

  greater_than++;
}
else if (ptr -> m_value <targ){
  less_than++;
}
  }
  ptr = ptr -> m_next;
}