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
#include

#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;
}