2.建立一个链表,每个结点包括:学号、姓名、性别、年龄。输入一个年龄,如果链表中的结点所包含的年龄等于此年龄,则将此结点删去。代码

以下是基于C语言的链表实现，实现了链表的插入、遍历和根据年龄删除结点的功能。

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

// 定义链表结构体
struct student {
    int id;
    char name[20];
    char gender;
    int age;
    struct student *next;
};

// 插入结点
struct student *insert(struct student *head, int id, char *name, char gender, int age) {
    struct student *p = (struct student *)malloc(sizeof(struct student));
    p->id = id;
    strcpy(p->name, name);
    p->gender = gender;
    p->age = age;
    p->next = head;
    head = p;
    return head;
}

// 遍历链表
void traverse(struct student *head) {
    struct student *p = head;
    while (p != NULL) {
        printf("id: %d, name: %s, gender: %c, age: %d\n", p->id, p->name, p->gender, p->age);
        p = p->next;
    }
}

// 根据年龄删除结点
struct student *delete_by_age(struct student *head, int age) {
    struct student *p = head;
    struct student *pre = NULL;
    while (p != NULL) {
        if (p->age == age) {
            if (pre == NULL) {
                head = p->next;
            } else {
                pre->next = p->next;
            }
            free(p);
            p = (pre == NULL ? head : pre->next);
        } else {
            pre = p;
            p = p->next;
        }
    }
    return head;
}

int main() {
    struct student *head = NULL;
    head = insert(head, 1, "Alice", 'F', 18);
    head = insert(head, 2, "Bob", 'M', 18);
    head = insert(head, 3, "Charlie", 'M', 20);
    head = insert(head, 4, "David", 'M', 19);
    printf("Before delete:\n");
    traverse(head);
    head = delete_by_age(head, 18);
    printf("After delete:\n");
    traverse(head);
    return 0;
}

代码中定义了一个 `student` 结构体，包含学号、姓名、性别和年龄四个成员变量，以及一个指向下一个结点的指针。通过 `insert` 函数实现链表结点的插入，通过 `traverse` 函数实现链表的遍历，通过 `delete_by_age` 函数实现根据年龄删除结点的功能。在主函数中，首先插入了四个结点，然后遍历了链表，接着根据年龄删除了年龄为 18 的结点，最后再次遍历链表，验证了删除操作的正确性。