分段故障删除节点

当我编译这个代码时，我得到了一个分段错误，我相信这是由这个块引起的。

EmployPtr iter;    
//Deletes nodes outside of range.
while(netSalary(iter)<45000 || netSalary(iter)>60000)
{
    EmployPtr nodeToDelete = iter;
    iter = iter->link;
    delete nodeToDelete;
}

我发现指针是非常混乱的，有一个指针不是指向内存中的有效对象，但我不确定如何解释它。我明白，我需要重新分配"下一个"(或"链接"我如何在我的代码中命名)指针的对象被删除之前，到下一个指针，对象被删除后。我试图用代码做到这一点，但我仍然得到segfault。有人能解释给我是怎么回事，并帮助我了解如何解决这个问题吗?

        EmployPtr nodeToDelete = iter->link;
        iter->link = nodeToDelete->link;
        delete nodeToDelete;

[包含其余代码，以防需要引用]

#include <fstream>
#include <iostream>
using namespace std;
struct Employee
{
    string firstN;
    string lastN;
    float salary;
    float bonus;
    float deduction;
    Employee *link;
};
typedef Employee* EmployPtr;
void insertAtHead( EmployPtr&, string, string, float, float,float );
void insert( EmployPtr&, string, string, float, float,float );
float netSalary( EmployPtr& );
int main()
{
    //Open file
    fstream in( "payroll.txt", ios::in );
    //Read lines
    string first, last;
    float salary, bonus, deduction;
    EmployPtr head = new Employee;
    //Inserts all the data into a new node in the linked list, creating a new node each time the loop executes.
    while( in >> first >> last >> salary >> bonus >> deduction)
        insert (head, first, last, salary, bonus, deduction);
    //Close file
    in.close();
    cout << "tttt-Salary in the range of ($45,000 - $60,000)-n" << "Printed in format: First Name, Last Name, Salary, Bonus, Deduction, Net Salary.nn";
    //Deletes all nodes in the list that are not between 45,000 and 65,000. It then prints the newly modified list.
    EmployPtr iter;
    for(iter = head; iter!= NULL; iter = iter->link)
    {
        //Deletes nodes outside of range.
        while(netSalary(iter)<45000 || netSalary(iter)>60000)
        {
            EmployPtr nodeToDelete = iter;
            iter = iter->link;
            delete nodeToDelete;
        }
        //Prints list.
        cout << iter->firstN << ", " << iter->lastN << ", " << iter->salary << ", " << iter->bonus << ", " << iter->deduction << ", " << netSalary(iter) <<endl;
    }
        return 0;
}
void insertAtHead(EmployPtr& head, string firstValue, string lastValue,
            float salaryValue, float bonusValue,float deductionValue)
{
    //method definition
}
void insert(EmployPtr& afterNode, string firstValue, string lastValue,
        float salaryValue, float bonusValue,float deductionValue)
{
    //method definition
}
float netSalary(EmployPtr& node)
{
   //method definition
}

    //Deletes nodes outside of range.
    while((netSalary(head)<45000 || netSalary(head)>60000) && head!=NULL)
    {
        EmployPtr nodeToDelete = head;
        head = head->link;
        delete nodeToDelete;
        nodeToDelete->link = head;
    }
        //Prints List
    EmployPtr iter;
    for(iter = head; iter!= NULL; iter = iter->link)
    {
        cout << iter->firstN << ", " << iter->lastN << ", " << iter->salary << ", " << iter->bonus << ", " << iter->deduction << ", " << netSalary(iter) <<endl;
    }