[置顶] c语言－指针实现链表增删改查

通过指针实现链表增删改查。

1.首先定义宏以及结构体作为数据结构使用。

#define LEN sizeof(struct student)

struct student{
    long num;
    float score;
    struct student *next;
};
int n;//为全局变量，本文件模块中各函数均可使用它

2.建立动态链表

struct student *create(void){//定义函数，此函数带回一个指向链表头的指针
    struct student *head;
    struct student *p1,*p2;
    n = 0;
    p1 = p2 = (struct student *)malloc(LEN);//开辟一个新单元
    scanf("%ld,%f",&p1->num, &p1->score);
    head = NULL;
    while (p1->num!=0) {
        n = n+1;
        if (n==1) {
            head = p1;
        }else {
            p2->next = p1;
        }
        p2 = p1;
        p1 = (struct student *)malloc(LEN);
        scanf("%ld,%f",&p1 -> num,&p1 -> score);
    }
    p2 -> next = NULL;
    return head;
}

3.输出链表

//输出链表
void print(struct student *head){
    struct student *p;

    printf("Now,These %d records are:\n",n);
    p = head;
    if (head!=NULL) {
        do {
            printf("%ld %5.1f\n",p->num,p->score);
            p = p->next;
        } while (p!=NULL);
    }
    printf("\n",n);
}

4.删除链表

struct student *del(struct student *head,long num){
    struct student *p1,*p2 = nullptr;
    if (head==NULL) {
        return head;
    }
    p1 = head;
    while (num!=p1->num&&p1->next!=NULL) {//p1指向的不是所要找的结点，并且后面还有结点
        p2 = p1;
        p1 = p1 -> next;
    }
    if (num == p1 -> num) {//找到了
        if (p1 == head) {
            head = p1 -> next;
        }else{
            p2 ->next = p1 -> next;
        }
        n = n - 1;
    }else {
        //找不到该结点
    }
    return head;
}

5.插入链表

struct student * insert(struct student * head,struct student *stud){
    struct student *p0,*p1,*p2 = nullptr;
    p1 = head;//使p1指向第一个结点
    p0 = stud;//p0指向要插入的结点

    if (head == NULL) {//原来的链表是空表
        head = p0;//p0指向的结点作为头结点
        p0 -> next = NULL;
    }else{
        while ((p0 -> num > p1 -> num) && (p1 -> next != NULL)) {
            p2 = p1;//使p2指向刚才p1指向的结点
            p1 = p1 -> next;//p1后移一个结点
        }
        if (p0 -> num <= p1 -> num) {
            if (head == p1) {
                head = p0;      //插到原来第一个结点之前
            }else {
                p2 -> next = p0;//插到p2指向的结点之后
            }
            p0 -> next = p1;
        }else{
            p1 -> next = p0;//插到最后的结点之后
            p0 -> next = NULL;
        }
    }
    n = n + 1;//结点数加1；
    return head;
}

6.主函数

int main(int argc, const char * argv[]) {

    struct student * head,stu;
    long del_num;

    printf("input records:(建立链表)\n");
    head = create();//建立链表，返回头指针
    print(head);//输出全部结点

    printf("input the deleted number(删除):\n");
    scanf("%ld",&del_num);
    head = del(head, del_num);//删除后链表的头地址
    print(head);//输出全部结点

    printf("input records(插入结点):\n");
    scanf("%ld,%f",&stu.num,&stu.score);
    head = insert(head, &stu);//插入一个结点，返回头结点地址
    print(head);//输出全部结点

    return 0;
}

7.测试结果截图