[数据结构与算法]双向循环链表的删除

建立双向循环链表，实现双向循环链表的删除操作。

#include <stdio.h>

int nodeNum = 5;

struct node
{
	int t;
	node * llink;
	node * rlink;
};

//建表 
struct node *creatlist()
{
	int i = 0;
	int t;
	struct node *head, *p, *q;
	//头结点
	scanf_s("%d", &t);
	head = new struct node;
	head->t = t;
	head->llink = 0;
	head->rlink = 0;
	q = head;

	for (i = 0; i < nodeNum - 1; i++) {
		scanf_s("%d", &t);
		p = new struct node;
		p->t = t;
		p->llink = q;
		p->rlink = 0;
		q->rlink = p;
		q = q->rlink;
	}

	q->rlink = head;
	head->llink = q;
	return head;
}

//删除
struct node *deleteOne(struct node *head, int i)
{
	if (head == 0) {
		printf("这是个空表\n");
		return head;
	}
	else if (i<0 || i>nodeNum) {
		printf("指定元素不存在\n");
		return head;
	}
	//可以删除
	struct node *q;
	if (i == 0) {
		q = head;
		head = head->rlink;
	}
	else if(i < nodeNum / 2){
		struct node *p;
		p = head;
		//从左往右找
		for (int j = 0; j < i - 1; j++) {
			p = p->rlink;
		}
		q = p->rlink;
		p->rlink = q->rlink;
		q->rlink->llink = p;
	}
	else {
		struct node *p;
		p = head;
		//从右往左找
		for (int j = 0; j < nodeNum - i - 1; j++) {
			p = p->llink;
		}
		q = p->llink;
		p->llink = q->llink;
		q->llink->rlink = p;
	}
	delete q;
	nodeNum--;
	return head;
}

//打印
void print(struct node *head)
{
	struct node *tmp = head;
	int i = 0;

	while (i < nodeNum)
	{
		printf("%d ", tmp->t);
		tmp = tmp->rlink;
		i++;
	}
	printf("\n");
}

//释放
void removeAll(struct node *head)
{
	struct node*p = head;
	for (int i = 0; i < nodeNum; i++) {
		p = head;
		head = head->rlink;
		delete p;
		nodeNum = 0;
	}
}

int main()
{
	int i;
	struct node *head = NULL;
	struct node *h = NULL;
	//创建链表
	printf("输入5个值\n");
	head = creatlist();

	//删除
	printf("删除第几个元素\n");
	scanf_s("%d", &i);
	i = i - 1;
	head = deleteOne(head, i);
	//head = deleteOne(h, i);//空链表

	//打印单链表
	printf("删除后的链表为：\n");
	print(head);

	//释放
	removeAll(head);

	return 0;
}

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