数据结构与算法笔记 lesson8 双向链表

双向链表结构

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

插入

s->next = p;

s->prior = p->prior;

p->prior->next=s;

p->prior=s;

删除

p->prior->next = p->next;

p->next->prior=p->prior;

free(p)

双向链表可以有效的提高算法的性能，用空间换取时间。

运用

输入一个数（支持负数），使得26个字母的排列顺序发生变化

例如输入3，  输出DEFGHIJKLMNOPQRSTUVWXYZABC

#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)
{
do
{
(*L) = (*L)->next;
} while (++i);
}
}
int main()
{
DuLinkList L;
int i,n;
InitList(&L);
printf("请输入一个整数\n");
scanf("%d", &n);
Caesar(&L, n);

for (i = 0; i < 26; i++)
{
L = L->next;
printf("%c", L->data);
}
return 0;
}