C语言链表：逆序建立单链表

#define _CRT_SECURE_NO_WARNINGS


#include<stdio.h>
#include<malloc.h>
#define LEN sizeof(struct Node)


struct Node
{
    int data;
    struct Node* Next;
};


typedef struct Node *PtrToNode;
typedef PtrToNode List;//表
typedef PtrToNode Position;//位置


List ReCreatTable(int n);//逆序建立单链表
void PrintTable(Position head);//遍历单链表
void Insert5th(Position head);//在单链表第五个元素前插入一个值为999的元素
void Delete5th(Position head);//删除单链表第五个元素

List ReCreatTable(int n)
{
    int  i;
    Position p, head;
    head = (Position)malloc(LEN);
    head->Next = NULL;
    for (i = 1; i <= n; i++)
    {
        p = (Position)malloc(LEN);
        printf("请输入元素:");
        scanf("%d", &p->data);
        p->Next = head->Next;
        head->Next = p;
    }
    return (head);
}


void PrintTable(Position head)
{
    Position s;
    s = head->Next;
    printf("链表:");
    while (s != NULL)
    {
        if (s->Next == NULL)
            printf("%d\n", s->data);
        else
            printf("%d ", s->data);
        s = s->Next;
    }
}


void Insert5th(Position head)
{
    Position P, TmpCell;
    TmpCell = (Position)malloc(LEN);
    P = head;
    int i;
    for (i = 0; i < 4; i++)
    {
        P = P->Next;
    }
    if (TmpCell == NULL)
        printf("Out of space!!!");
    TmpCell->data = 999;
    TmpCell->Next = P->Next;
    P->Next = TmpCell;
}


void Delete5th(Position head)
{
    Position P, TmpCell;//TemCell是删除元素
    P = head;
    int i;
    for (i = 0; i < 4; i++)
    {
        P = P->Next;
        TmpCell = P->Next;
    }
    P->Next = TmpCell->Next;
    free(TmpCell);
}


int main()
{
    int n;
    Position head;
    printf("请输入链表元素个数:");
    scanf("%d", &n);
    head = ReCreatTable(n);
    PrintTable(head);
    printf("在第五个元素前插入999后");
    Insert5th(head);
    PrintTable(head);
    printf("删除第五个元素后");
    Delete5th(head);
    PrintTable(head);
    return 0;
}