c - 删除节点后打印结构链表时出错

Question

我正在制作一个员工链表。做所有常见的事情，添加、搜索和更新。我正在尝试使删除功能正常工作，但据称删除节点后我无法打印链接列表以查看。这是完整的代码，以及错误消息。感谢您花时间阅读本文。

LinkedList.exe 中 0x0FA4FB53 (msvcr120d.dll) 处的未处理异常:0xC0000005:读取位置 0xFEEEFEEE 的访问冲突。

#include <stdlib.h>
#include <stdio.h>
#include <string.h>


#define ID_LENGTH 25
#define NAME_LENGTH 25
#define address_LENGTH 25
#define department_LENGTH 25
#define joinDate_LENGTH 25
#define email_LENGTH 30
int mymenu;

//Create employee Structure
typedef struct employee{
    char* ID;
    char* name;
    char* department;
    char* address;
    char* joinDate;
    double salary;
    char* email;
    struct employee *next;
}employee;

//Declare Function Prototypes
int login();
int Menu();
void Add(struct employee *head);
void search(struct employee *head, char*);
void update(struct employee *head, char*);
void outputList();
struct employee* searchForEmployee(char* );
employee* new_employee(char*, char*, char*, char*, char*, double, char*);
employee* insert_by_employee(employee*, employee*);
void removeEmployee(char *);
void print_list(employee*); // prints out the LinkedList


employee* head = NULL; 
employee* tail = NULL;
employee* temp = NULL;
employee* current = NULL;


//this stores the employee that comes before the employee that is found by the searchforEmployee
struct employee *empBeforeEmptoDelete = NULL;

int main() {
    int num = 0;
    int MenuChoice = 0;

    Menu();


    FILE *in;
    char* ID = (char*)malloc(sizeof(char*) * ID_LENGTH);
    char* name = (char*)malloc(sizeof(char*) * NAME_LENGTH);
    char* department = (char*)malloc(sizeof(char*) * department_LENGTH);
    char* address = (char*)malloc(sizeof(char*) * address_LENGTH);
    char* joinDate = (char*)malloc(sizeof(char*) * joinDate_LENGTH);
    double salary = 0;
    char* email = (char*)malloc(sizeof(char*) * email_LENGTH);


    if ((in = fopen("Employees.txt", "r")) == NULL) //Did the file successfully open?
    {
        printf("The input file failed to open.\n");
        printf("Program cannot continue. Exiting. . .\n");
        return 1; //Exit Program
    }


    while (!feof(in)) //Check for file end
    {
        //Read first data value to kickstart.
        if (fscanf(in, "%s %s %s %s %s %lf %s", ID, name, department, address, joinDate, &salary, email) == EOF) {
            break;
        }

        employee* hold = new_employee(ID, name, department, address, joinDate, salary, email);
        head = insert_by_employee(head, hold);

    }

    //3. ------Print the new List------
    //print_list(head);
    do
    {
        switch (MenuChoice = Menu())
        {
        case 1:
        {
            Add(head);
            break;
        }
        case 2:
        {
            char text[10];
            printf("Enter the text to search for :");
            scanf("%s", text);
            //search(head, text);
            searchForEmployee(text);
            break;
        }
        case 3:
        {
            char text[10];
            printf("Enter the ID to update for :");
            scanf("%s", text);
            update(head, text);
            break;
        }
        case 4:
        {
            outputList();
            char text[10];
            printf("Enter the ID to remove :");
            scanf("%s", text);
            removeEmployee(text);
            outputList();
            break;

        }
        case 5:
        {
            print_list(head);
            break;
        }
        case 6:
        {

            break;
        }
        case 7:
        {
            break;
        }
        case 8:
        {
            exit(0);
            break;
        }
        default:
        {
            printf("\nInvalid Selection");
            break;
        }
        }
    } while (MenuChoice < 8);

    system("Pause");
    printf("\n\n\n");
    return 1; //Exit Success
}
employee* new_employee(char* id, char* name, char* department, char* address, char* joinDate, double salary, char* email) {

    //Create new employee and malloc space
    employee* new = (employee*)malloc(sizeof(struct employee));
    new->ID = (char*)malloc(sizeof(char) * ID_LENGTH);
    new->name = (char*)malloc(sizeof(char) * NAME_LENGTH);
    new->department = (char*)malloc(sizeof(char) * department_LENGTH);
    new->address = (char*)malloc(sizeof(char) * address_LENGTH);
    new->joinDate = (char*)malloc(sizeof(char) * joinDate_LENGTH);
    new->email = (char*)malloc(sizeof(char) * email_LENGTH);



    //Set data
    strcpy(new->ID, id);
    strcpy(new->name, name);
    strcpy(new->department, department);
    strcpy(new->address, address);
    strcpy(new->joinDate, joinDate);
    new->salary = salary;
    strcpy(new->email, email);
    //Retun a pointer to the node
    return new;

}

//Inserts new node into an alphabetically sorted linked list.
employee* insert_by_employee(employee* head, employee* new)
{
    employee* current = NULL;
    current = head;
    if (current == NULL || strcmp(current->department, new->department) > 0)
    {
        new->next = current;
        return new;
    }
    else {

        while (current->next != NULL && strcmp(current->next->department, new->department) < 0)
        {

            current = current->next;
        }
    }
    new->next = current->next;
    current->next = new;
    return head;

}
struct employee* searchForEmployee(char* id){
    struct employee *empIterator = head;
    char i[] = "Employee ID";
    char n[] = "Name";
    char a[] = "Address";
    char d[] = "Department";
    char jd[] = "Join Date";
    char s[] = "Salary";
    char em[] = "Email";

    while (empIterator != NULL){
        int isEqual = strcmp(empIterator->ID, id);//if the passed in ID is equla to the ID of the node then isEqual will ring true

        if (!isEqual){

            printf("Employee Found\n");
            printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
            printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", empIterator->ID, empIterator->name, empIterator->address, empIterator->department, empIterator->joinDate, empIterator->salary, empIterator->email);
            //printing out the current node which is the desired employee
            printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
            return empIterator;
        }
        empBeforeEmptoDelete = empIterator->next;

        empIterator = empIterator->next;
    }
    printf("%s was not found\n\n", id);
    return NULL;
}
void print_list(employee* head)
{
    employee* current;
    current = head;
    char i[] = "Employee ID";
    char n[] = "Name";
    char a[] = "Address";
    char d[] = "Department";
    char jd[] = "Join Date";
    char s[] = "Salary";
    char em[] = "Email";


    //Header
    printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);
    printf("--------------------------------------------------------------------------------------------------------------------------------------------\n");


    while (current != NULL)
    {
        printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", current->ID, current->name, current->address, current->department, current->joinDate, current->salary, current->email);
        current = current->next;
    }
    printf("-------------------------------------------------------------------------------------------------------------------------------------------\n");


    return;
}
int login()
{

    char username[7];
    char password[7];

    printf("\nPlease enter your Username: ");
    scanf("%s", username);
    printf("\nPlease enter your Password: ");
    scanf("%s", password);

    struct login{
        char name[7];
        char password[7];

    };
    struct login details[3];
    fflush(stdin);

    FILE *file;
    file = fopen("login.txt", "r");
    if (file == NULL){
        printf("Can not open the file\n");
        exit(-1);
    }
    fflush(stdin);

    for (int i = 0; i < 3; i++){
        fscanf(file, "%s %s\n", details[i].name, details[i].password);
    }


    for (int i = 0; i < 3; i++){
        if ((strcmp(details[i].name, username) == 0) && (strcmp(details[i].password, password) == 0))
        {
            printf("\nWelcome ");
            Menu();
        }
        fflush(stdin);
    }
}
int Menu()
{
    int Choice = 0;

    do{

        printf("1. Add\n");
        printf("2. Show\n");
        printf("3. Update\n");
        printf("4. Delete\n"); // Write a Function for this
        printf("5. Departments\n");
        printf("6. Employee Report\n");
        printf("7. \n");
        printf("8. Exit\n\n\n\t\tSELECTION = ");

        fflush(stdin);

        scanf("%d", &Choice);
        fflush(stdin);
    } while (Choice < 0 || Choice > 8);

    return(Choice);
}
void Add()
{

    char* ID = (char*)malloc(sizeof(char*) * ID_LENGTH);
    char* name = (char*)malloc(sizeof(char*) * NAME_LENGTH);
    char* department = (char*)malloc(sizeof(char*) * department_LENGTH);
    char* address = (char*)malloc(sizeof(char*) * address_LENGTH);
    char* joinDate = (char*)malloc(sizeof(char*) * joinDate_LENGTH);
    double salary = 0;
    char* email = (char*)malloc(sizeof(char*) * email_LENGTH);


    printf("\nEnter the ID : ");
    scanf("%s", ID);
    printf("\nEnter the new employee name : ");
    scanf("%s", name);
    printf("\nEnter their address : ");
    scanf("%s", address);
    printf("\nEnter their department : ");
    scanf("%s", department);
    printf("\nEnter their start date : ");
    scanf("%s", joinDate);
    printf("\nEnter their salary : ");
    scanf("%lf", &salary);
    printf("\nEnter their email : ");
    scanf("%s", email);


    employee* hold = new_employee(ID, name, department, address, joinDate, salary, email);
    head = insert_by_employee(head, hold);
}
void search(struct employee *head, char *crit)//This function takes in the head pointer and a character array pointer
{
    int choice;//menu choice tracker

    //arrays to hold the header heads
    char i[] = "Employee ID";
    char n[] = "Name";
    char a[] = "Address";
    char d[] = "Department";
    char jd[] = "Join Date";
    char s[] = "Salary";
    char em[] = "Email";

    //sub menu to filter by ID and Name searches
    printf("\nSearch by ");
    printf("\n1 : ID");
    printf("\n2 : Name\n");
    scanf("%d", &choice);

    //if the user wants to search by ID
    if (choice == 1){
        while (head != NULL)
        {
            //compare the ID to the criteria. If its the same then execute this if
            if ((strcmp(head->ID, crit) == 0))
            {
                //print that we found the employee
                printf("Employee Found\n");
                printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
                printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
                //printing out the current node which is the desired employee
                printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                return;
            }
            head = head->next;//increments the node until we get to the end of the Linked List
        }
        printf("Employee not found\n");//Else there is no Employee with an ID of the entered criteria
    }
    //if the user wants to search by Name
    else if (choice == 2){
        while (head != NULL)
        {
            //compare the Name to the criteria. If its the same then execute this if
            if ((strcmp(head->name, crit) == 0))
            {
                //print that we found the employee
                printf("Employee Found\n");
                printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
                printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
                //printing out the current node which is the desired employee
                printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                return;
            }
            head = head->next;//increments the node until we get to the end of the Linked List
        }
        printf("Employee not found\n");//Else there is no Employee with an Name of the entered criteria
    }
    else
        printf("Bad input");//Otherwise the user entered a choice out of the range of our handled input
}
void update(struct employee *head, char *crit)//This function takes in the head pointer and a character array pointer
{


    //arrays to hold the header heads
    char i[] = "Employee ID";
    char n[] = "Name";
    char a[] = "Address";
    char d[] = "Department";
    char jd[] = "Join Date";
    char s[] = "Salary";
    char em[] = "Email";

    char id[25];
    char name[25];
    char address[25];
    char department[25];
    char joinDate[25];
    double salary;
    char email[25];


    //if the user wants to search by ID
        while (head != NULL)
        {
            //compare the ID to the criteria. If its the same then execute this if
            if ((strcmp(head->ID, crit) == 0))
            {
                //print that we found the employee
                printf("Employee Found\n");
                printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
                printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
                //printing out the current node which is the desired employee
                printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");

                printf("\nEnter the ID : ");
                scanf("%s", id);
                printf("\nEnter the new employee name : ");
                scanf("%s", name);
                printf("\nEnter their address : ");
                scanf("%s", address);
                printf("\nEnter their department : ");
                scanf("%s", department);
                printf("\nEnter their start date : ");
                scanf("%s", joinDate);
                printf("\nEnter their salary : ");
                scanf("%lf", &salary);
                printf("\nEnter their email : ");
                scanf("%s", email);

                strcpy(head->ID, id);
                strcpy(head->name, name);
                strcpy(head->department, department);
                strcpy(head->address, address);
                strcpy(head->joinDate, joinDate);
                head->salary = salary;
                strcpy(head->email, email);

                printf("Employee Found\n");
                printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
                printf("----------------------------------------------------------------------------------------------------------------------------------------------------\n");
                printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", head->ID, head->name, head->address, head->department, head->joinDate, head->salary, head->email);
                //printing out the current node which is the desired employee
                printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");

                return;
            }
            head = head->next;//increments the node until we get to the end of the Linked List
        }
        printf("Employee not found\n");//Else there is no Employee with an ID of the entered criteria
    }
void outputList(){
    char i[] = "Employee ID";
    char n[] = "Name";
    char a[] = "Address";
    char d[] = "Department";
    char jd[] = "Join Date";
    char s[] = "Salary";
    char em[] = "Email";

    struct employee * employees = head;
    printf("Employees Entered\n\n");
    while (employees != NULL){
        printf("Employee Found\n");
        printf("\n\n|%15s | %15s | %15s | %15s | %15s| %15s | %15s|\n", i, n, a, d, jd, s, em);//header formatting
        printf("|%15s | %15s | %15s |%15s | %15s | %15.2lf| %25s\n", employees->ID, employees->name, employees->address, employees->department, employees->joinDate, employees->salary, employees->email);
        printf("-----------------------------------------------------------------------------------------------------------------------------------------------------\n");

        employees = employees->next;
    }
}
void removeEmployee(char* empID){

    struct employee* empToDelete = NULL;

    empToDelete = searchForEmployee(empID);

    if (empToDelete != NULL){

        printf("%s was deleted\n\n", empID);

        if (empToDelete == head){

            head = empToDelete->next;
        }
        else{
            empBeforeEmptoDelete->next = empToDelete->next;
        }

        free(empToDelete);
    }
    else{
        printf("%s was not found", empID);
    }
}

Answer 1

在 removeEmployee(char* empID) 函数中:
情况:当要删除的节点不是头节点时；

这里首先要保存delete_node的previous_node指针，然后将previous_node->next设置为delete_node->next 并删除 delete_node。

你还没有保存previous_node的指针。

empBeforeEmptoDelete->next = empToDelete->next;