链表的增删改查

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

struct node {
    char name[20];
    int age;
    struct node* next;
};

// 添加节点到链表末尾
void addstudent(struct node** head, const char* name, int age) {
    struct node* newstudent = (struct node*)malloc(sizeof(struct node));
    if (newstudent == NULL) {
        printf("内存分配失败\n");
        return;
    }
    strcpy(newstudent->name, name);
    newstudent->age = age;
    newstudent->next = NULL;
    if (*head == NULL)
        *head = newstudent;
    else {
        struct node* temp = *head;
        while (temp->next != NULL) {
            temp = temp->next;
        }
        temp->next = newstudent;
    }
}

// 根据姓名查询节点
struct node* findstudent(struct node* head, const char* name) {
    struct node* p = head;
    while (p != NULL && strcmp(p->name, name) != 0) {
        p = p->next;
    }
    if (p == NULL)
        return NULL;
    else
        return p;
}

// 修改节点信息
void updatestudent(struct node* head, const char* oldname, const char* newname, int newage) {
    struct node* student = findstudent(head, oldname);
    if (student != NULL) {
        strcpy(student->name, newname);
        student->age = newage;
    } else
        printf("未找到名为%s的学生\n", oldname);
}

void deletestudent(struct node** head, const char* name) {
    struct node* temp = *head;
    struct node* prev = NULL;
    // 如果头节点就是要删除的节点
    if (temp != NULL && strcmp(temp->name, name) == 0) {
        *head = temp->next;
        free(temp);
        return;
    }
    // 查找要删除的节点，记录前一个节点
    while (temp != NULL && strcmp(temp->name, name) != 0) {
        prev = temp;
        temp = temp->next;
    }
    // 未找到
    if (temp == NULL) {
        return;
    }
    prev->next = temp->next;
    free(temp);
}

// 打印链表
void printlist(struct node* head) {
    struct node* temp = head;
    while (temp != NULL) {
        printf("%s  %d\n", temp->name, temp->age);
        temp = temp->next;
    }
}

// 释放链表所有节点的内存
void freelist(struct node** head) {
    struct node* temp;
    while (*head != NULL) {
        temp = *head;
        *head = (*head)->next;
        free(temp);
    }
    *head = NULL; // 确保头指针悬空
}

int main() {
    struct node* head = NULL;

    // 添加学生信息
    addstudent(&head, "张三", 20);
    addstudent(&head, "李四", 21);
    addstudent(&head, "王五", 22);

    // 打印链表
    printf("初始链表信息：\n");
    printlist(head);

    // 修改学生信息
    updatestudent(head, "李四", "赵六", 23);
    printf("\n修改后链表信息：\n");
    printlist(head);

    // 删除学生信息
    deletestudent(&head, "王五");
    printf("\n删除后链表信息：\n");
    printlist(head);

    // 释放链表内存
    freelist(&head);

    return 0;
}