基础数据结构——双链表

//带头节点双链表
#include<iostream>
#include<stdlib.h>
using namespace std;
typedef int type;
typedef struct DNode{
	type data;
	struct DNode *prior;
	struct DNode *next;
} DNode ,*DLinkNode; 
//初始化头节点 
void init(DLinkNode &head){
	head=(DLinkNode)malloc(sizeof(DNode));
	head->prior=NULL;
	head->next=NULL;
}
//头插法
DLinkNode createR(){
	DLinkNode head,s;
	init(head);
	type x;
	cin>>x;
	while(x!=-1){
		s=(DLinkNode)malloc(sizeof(DNode));
		s->data=x;
		s->next=head->next;
		s->prior=head;
		head->next=s;
		cin>>x;
	}
	return head;
}
//尾插法
DLinkNode createF(){
	DLinkNode head,s,p;
	init(head);
	p=head;   //一点要初始化之后在赋值  
	type x;
	cin>>x;
	while(x!=-1){
		s=(DLinkNode)malloc(sizeof(DNode));
		s->data=x;
		s->next=p->next;
		p->next=s; 
		s->prior=p;
		p=s;
		cin>>x;
	}
	return head;
} 
//判断链表是否为空
int isEmpty(DLinkNode head){
	return head->next==NULL;
} 
//返回链表长度
int length(DLinkNode head){
	
	DLinkNode p=head->next;
	int len=0;
	while(p){
		len++;
		p=p->next;
	}
	return len;
} 
//销毁链表 
void destroy(DLinkNode &head){
		DLinkNode p;
		while(head){
			p=head->next;
			free(head);
			head=p;
		} 
}
//在指定位置插入元素
int insertElem(DLinkNode head,int p,type x){
		if(p<0||p>length(head)) return -1;
		DLinkNode q=head->next;
		int i=0;
		while(q&&i!=p-1){
			q=q->next;
			i++;
		}
		DLinkNode s=(DLinkNode)malloc(sizeof(DNode));
		s->data=x;
		s->next=q->next;
		s->prior=q;
		q->next=s;
		return 1;
} 
//删除指定位置的元素
int deleteElem_p(DLinkNode head,int p){
	if(isEmpty(head)||p<0||p>=length(head)) return -1;
	DLinkNode q=head->next;
	int i=0;

	while(q->next&&i!=p){
		q=q->next; 
		i++;
	}
	q->prior->next=q->next;
	free(q);
	return 1;
} 
//删除指定链表中的指定值
int deleteElem(DLinkNode head,int x){
	if(isEmpty(head)) return -1;
	DLinkNode q=head->next;
	DLinkNode l,p=head;
	while(q->next){
		if(q->data==x){
			l=q;
			p->next=l->next;
			l->next->prior=p;
			q=p->next;
			free(l);
		}
		else{
			p=p->next;
			q=q->next;
		}
	}
	if(q->data==x){ //最后一个结点是要删除的结点 
		p->next=NULL; 
	}
	return 1; 
} 
//查找指定元素第一次出现的位置
int findElem(DLinkNode head,int x){
	if(isEmpty(head)) return -1;
	DLinkNode q=head->next;
	int i=0;
	while(q&&q->data!=x) i++,q=q->next;
	if(q==NULL) return -1;
	return i;	
} 
//返回指定位置的元素
type findElem_p(DLinkNode head,int p){
	if(isEmpty(head)||p<0||p>=length(head))	return -1;
	DLinkNode q=head->next;
	int i=0;
	while(q&&i!=p) i++,q=q->next;
	if(q==NULL) return -1;
	return q->data;
}
//打印链表
void print(DLinkNode head){
	if(isEmpty(head)) return ;
	DLinkNode p=head->next;
	while(p){
		cout<<p->data<<" ";
		p=p->next;
	}
	cout<<endl;
} 
int main(){
	//DLinkNode head=createR();
	//print(head);
	DLinkNode head=createF();
	print(head);
	//insertElem(head,3,99);
	print(head);
	//deleteElem_p(head,3);
	print(head);
	//deleteElem(head,2);
	//print(head);
	cout<<findElem(head,2)<<endl;
	cout<<findElem_p(head,4)<<endl;
	cout<<length(head)<<endl;
	destroy(head);
	print(head);
	return 0;
}