链表初解（二）——双链表的创建、删除、插入

下面是基本的双链表操作，由于双链表有两个方向，所以在删除和插入节点时，可以节省一个指针，只用一个链表上的指针和一个待操作的指针即可完成插入和删除；同时也要注意在编写双链表时对情况的判断要仔细，否则很容易出错~

#include<iostream>
using namespace std;

typedef struct student
{
	int data;
	struct student *next;
	struct student *pre;
}dnode;

//建立双链表
dnode *create()
{
	dnode *head, *p, *s;
	int x;
	head = (dnode *)malloc(sizeof(dnode));
	p = head;
	cout<<"\nInput the data : ";
	while(1)
	{
		if(scanf("%d", &x) != EOF && x != 0)
		{
			s = (dnode *)malloc(sizeof(dnode));
			s->data = x;
			p->next = s;
			s->pre = p;
			p = s;
		}
		else break;
	}
	head = head->next;
	head->pre = NULL;
	p->next = NULL;
	return head;
}

//双链表删除节点
dnode *del(dnode *head, int num)
{
	dnode *p1;
	p1 = head;
	while(num != p1->data && p1->next != NULL)
		p1 = p1->next;
	if(num == p1->data)
	{
		if(head == p1)
		{
			head = head->next;
			head->pre = NULL;
		}/*此处的处理与单链表不同，因为双链表有两个方向，所以在定义时仅定义一个指针，
		这使得当出现删除链表尾部时，由于NULL没有前驱，导致无法连接，所以要分开讨论。*/
		else if(p1->next == NULL) p1->pre->next = NULL;
		else
		{//p1为最后一个节点，如没有上一个分支，则第二个语句会出错。
			p1->pre->next = p1->next;
			p1->next->pre = p1->pre;
		}
		free(p1);	//释放
	}
	else cout<<"There is no %d "<<num;
	return head;
}

//双链表插入节点
dnode *insert(dnode *head, int num)
{
	dnode *p0, *p1;
	p1 = head;
	p0 = (dnode *)malloc(sizeof(dnode));
	p0->data = num;
	while(num > p1->data && p1->next != NULL)
		p1 = p1->next;
	if(num <= p1->data)
	{
		if(head == p1)
		{
			p0->next = p1;
			p1->pre = p0;
			head = p0;
		}
		else
		{
			p1->pre->next = p0;
			p0->pre = p1->pre;
			p0->next = p1;
			p1->pre = p0;
		}
	}
	else
	{//插入尾部~
		p1->next = p0;
		p0->next = NULL;
		p0->pre = p1;
	}
	return head;
}

//计算表长
int length(dnode *head)
{
	int n = 0;
	while(head != NULL)
	{
		head = head->next;
		n++;
	}
	return n;
}
//打印双链表
void print(dnode *head)
{
	int n = length(head);
	cout<<"Output the DoubleList ("<<n<<" records~) : ";
	while(head != NULL)
	{
		if(head->next == NULL) cout<<head->data<<endl;
		else cout<<head->data<<"<->";
		head = head->next;
	}
}
//排序函数同单链表，此处省略了~，默认输入为递增哈~
int main()
{
	dnode *head;
	//创建
	head = create();
	print(head);
	//删除
	int numD;
	cout<<"\nDelete : ";
	cin>>numD;
	print(del(head, numD));
	//插入
	int numS;
	cout<<"\nInsert : ";
	cin>>numS;
	print(insert(head, numS));
	return 0;
}

Ps：仅供参考~~

链表初解（二）——双链表的创建、删除、插入,布布扣,bubuko.com

链表初解（二）——双链表的创建、删除、插入

原文：http://blog.csdn.net/zenail501129/article/details/22445947