线性表-双向链表

双向链表

结点结构：

typedef struct DualNode
{
    ElemType data;
    struct DualNode *prior;  //前驱结点
    struct DualNode *next;   //后继结点
}DualNode, *DuLinkList;

插入操作：

s->next = p;
s->prior = p->prior;
p->prior->next = s;
p->priot = s;

删除操作：

p->prior->next = p->next;
p->next->prior = p->prior;
free(p);

题目实践：

要求实现用户输入一个数使得26个字母的排列发生变化，例如

输入:3
输出:DEFGHIJKLMNOPQRSTUVWXYZABC
输入:-3
输出:XYZABCDEFGHIJKLMNOPQRSTUVW

代码：

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

#define OK  1
#define ERROR 0

typedef char ElemType;
typedef int Status;

typedef struct DualNode
{
    ElemType data;
    struct DualNode *prior;
    struct DualNode *next;
}DualNode, *DuLinkList;

Status InitList(DuLinkList *L)
{
    DualNode *p,*q;
    int i;
    *L = (DuLinkList)malloc(sizeof(DualNode));
    if(!(*L))
    {
        return ERROR;
    }
    (*L)->next = (*L)->prior = NULL;
    p = (*L);
    for(i=0;i<26;i++)
    {
        q = (DualNode *)malloc(sizeof(DualNode));
        if(!q)
        {
            return ERROR;
        }
        q->data = 'A'+i;
        q->prior = p;
        q->next = p->next;
        p->next = q;
        p = q;
    }
    p->next = (*L)->next;
    (*L)->next->prior = p;
    
    return OK;
    
}
void Caesar(DuLinkList *L,int i)
{
    if(i>0)
    {
        do
        {
            (*L) = (*L)->next;
        }while(--i);
    }
    if(i<0)
    {
    	(*L) = (*L)->next;  //注意此时*L不在环内，要先把它加入环中
        do
        {
            (*L) = (*L)->prior;
    	}while(i++);
    }
}
int main(){
    DuLinkList L;
    int i,n;
    InitList(&L);
    printf("请输入一个整数：");
    scanf("%d",&n);
//    printf("\n");
    Caesar(&L,n);
    for(i=0;i<26;i++){
        L = L->next;
        printf("%c",L->data);
    }
    return 0;
}