雙向鏈表的基本操作 C語言

#include<stdio.h>
#include<stdlib.h>
typedef struct node* DNode;
struct node {
    int data;
    DNode prior; //前面數據地址
    DNode next;  //后面數據地址
}; 
//創建雙向鏈表
void CreatNode(DNode *head) {
    DNode s;  //新節點指針
    char e;
    (*head) = (DNode)malloc(sizeof(struct node));//頭結點
    (*head)->prior = (*head);  //初始頭結點的前驅和后驅都指向自己
    (*head)->next = (*head);
    printf("輸入數據\n");
    scanf("%c", &e);
    while (e!='\n')
    {
        s = (DNode)malloc(sizeof(struct node)); //新節點分配空間
        s->data = e;
        s->prior = (*head);   //新節點的prior連前一個結點
        s->next = (*head)->next; //新節點的next連后邊結點
        (*head)->next->prior = s; //后一個結點的prior連新結點
        (*head)->next = s;  //新節點前面的next連新結點
        scanf("%c", &e);
    }
}
//向后遍歷輸出
void PrintList1(DNode L) {
    DNode p;
    p = L;
    p = p->next;
    while (p != L) {
        printf("%c", p->data);
        p = p->next;
    }
    printf("\n");
}
//向前遍歷輸出
void PrintList2(DNode L) {
    DNode p;
    p = L->prior;
    while (p != L) {
        printf("%c", p->data);
        p = p->prior;
    }
    printf("\n");
}
//查找第i處數據的地址
DNode FindPosition(DNode L,int i) {
    int j = 0;
    DNode p = L;
    while (p->next != L&&j < i) {
        p = p->next;
        j++;
    }
    return p;
}
//插入
void InsertList(DNode L) {
    DNode s,p;  //s為新結點 p為新節點前一個結點
    int i;
    char e;
    printf("在第幾處插入:\n");
    scanf("%d", &i);
    getchar();
    printf("插入什么數據:\n");
    scanf("%c", &e);
    p = FindPosition(L, i-1);  //新節點前一個結點地址
    s = (DNode)malloc(sizeof(struct node));//申請新節點空間
    s->data = e;
    s->prior = p;  //新節點的prior連上前一個結點
    s->next = p->next;  //新節點的next連上后一個結點
    p->next->prior = s;  //新節點后的結點的prior連上新結點
    p->next = s;         //新節點前的結點的next連上新結點
}
//刪除
 void DeleteList(DNode L){
     DNode s,p;  //s為新結點 p為要刪除的結點
     int i;
     printf("刪除第幾處的數據:\n");
     scanf("%d", &i);
     p = FindPosition(L, i); //要刪除結點的地址
     p->prior->next = p->next;  //要刪除的結點的前一個結點的next，連上要刪結點后的結點
     p->next->prior = p->prior;//要刪除結點的后一個結點的prior，連上要刪結點的前一個結點
     free(p);
 }


int main() {
    DNode list;
    CreatNode(&list);
    //PrintList1(list);
    PrintList2(list);
    InsertList(list);
    PrintList2(list);
    DeleteList(list);
    PrintList2(list);
}