动态链表节点删除

链表是一种常见的重要的数据结构，他是动态的进行存储分配的一种结构。

#include <malloc.h>
#include <stdio.h>
#include <stdlib.h>               //动态分配内存引入
#define NC sizeof(struct student) //宏定义内存大小
struct student                    //定义结构体数据类型
{
    int num;              //学号
    int score;            //分数
    struct student *next; //下一个结点地址
};
int N; //全局变量,表示链表节点数
//函数声明
struct student *creat(void); //创建链表
void print();                //打印函数
struct student *del();       //删除函数
//主函数
int main()
{
    struct student *stu, *p;
    int num; //定义需删除的数据的num号

    stu = creat(); //创建链表,返回头指针head
    p = stu;
    print(p); //打印数据
    printf("Please input the num to delete:");
    scanf("%d", &num);
    print(del(p, num)); //调用del函数后,返回头指针,重新传递给print函数打印出数据
    printf("\n\n");
    system("pause"); //就是暂停程序的执行，等待任意健继续执行,查看结果,防止一闪而过
    return 0;
}
//创建链表
struct student *creat(void)
{
    struct student *p1, *p2, *head;
    p1 = p2 = (struct student *)malloc(NC); //动态分配内存大小
    printf("please input num :");
    scanf("%d", &p1->num);
    printf("please input score :");
    scanf("%d", &p1->score);
    head = NULL; //初始化
    N = 0;
    while (p1->num) {
        N++;
        if (N == 1) {
            head = p1;
        } else {
            p2->next = p1;
        }
        p2 = p1;
        p1 = (struct student *)malloc(NC);
        printf("\nplease input num :");
        scanf("%d", &p1->num);
        printf("please input score :");
        scanf("%d", &p1->score);
    }
    p2->next = NULL;
    return head;
}
//输出链表
void print(struct student *head)
{
    struct student *p;
    printf("\nThere are %d records!\n", N);
    p = head;
    if (head) {
        do {
            printf("学号为%d的同学成绩是:%d\n", p->num, p->score);
            p = p->next;
        } while (p); // p为NULL时停止循环
    }
}
//删除结点
struct student *del(struct student *head, int num) //形参
{
    struct student *p1, *p2;
    if (head == NULL) {
        printf("\nThis is a NULL chart!");
        goto END; //判断链表为空,直接跳转到返回语句
    }
    p1 = head; //不为空赋值给p1
    while (p1->num != num && p1->next != NULL) {
        p2 = p1;
        p1 = p1->next;
    }
    if (num == p1->num) {
        if (p1 == head) {
            /* code */
            head = p1->next;
        } else {
            p2->next = p1->next;
        }
        printf("\nDelete num:%d data success!", num);
        N--;
    } else {
        printf("\nnum:%d not been found!", num);
    }
END:
    return head;
}