Day 63 双向循环链表

#include
#include
#include
 
typedef struct node{
	struct node *prev;
	struct node *next;
	int data;
}Node;
 
Node *buylistnode(int data){
	Node *newnode=(Node *)malloc(sizeof(Node));
	if(newnode==NULL){
		printf("malloc error");
		exit(-1);
	}
	newnode->prev=newnode->next=NULL;
	newnode->data=data;
	return newnode;
}
 
Node *listinit(){
	Node *plist=buylistnode(0);
	plist->prev=plist->next=plist;
	return plist;
}
 
void listpushback(Node *plist,int data){
	if(plist==NULL){
		printf("This list is empty.\n");
		return;
	}
	Node *newnode=buylistnode(data);
	Node *tail=plist->prev;
	tail->next=newnode;
	newnode->prev=tail;
	newnode->next=plist;
	plist->prev=newnode;
}
 
void listpopback(Node *plist){
	if(plist==NULL){
		printf("This list is empty.\n");
		return;
	}
	if(plist->next!=plist){
		printf("This list is not only head.\n");
	}
	Node *tail=plist->prev;
	Node *tailprev=tail->prev;
	tailprev->next=plist;
	plist->prev=tailprev;
	free(tail);
	tail=NULL;
}
 
void listpushfront(Node *plist,int data){
	if(plist==NULL){
		printf("This list is empty.\n");
	}
	Node *newnode=buylistnode(data);
	Node *first=plist->next;
	plist->next=newnode;
	newnode->prev=plist;
	newnode->next=first;
	first->prev=newnode;
}
 
void listpopfront(Node *plist){
	if(plist==NULL){
		printf("This list is empty.\n");
		return;
	}
	if(plist->next!=plist){
		printf("List is not only head\n");
	}
	Node *first=plist->next;
	Node *second=first->next;
	plist->next=second;
	second->prev=plist;
	free(first);
	first=NULL;
}
 
Node *listfind(Node *plist,int data){
	if(plist==NULL){
		printf("This list is empty.\n");
		return NULL;
	}
	Node *cur=plist->next;
	while(cur!=plist){
		if(cur->data==data){
			return cur;
		}
		cur=cur->next;
	}
	return NULL;
}
 
void listinsert(Node *pos,int data){
	if(pos==NULL){
		printf("List is empty.\n");
		return;
	}
	Node *newnode=buylistnode(data);
	Node *posprev=pos->prev;
	posprev->next=newnode;
	newnode->prev=posprev;
	newnode->next=pos;
	pos->prev=newnode;
}
 
void listerase(Node *pos){
	if(pos==NULL){
		printf("List is empty.\n");
		return;
	}
	Node *posprev=pos->prev;
	Node *posnext=pos->next;
	posprev->next=posnext;
	posnext->prev=posprev;
	free(pos);
	pos=NULL;
}
 
void listprint(Node *plist){
	if(plist==NULL){
		printf("List is empty.\n");
		return;
	}
	Node *cur=plist->next;
	while(cur!=plist){
		if(cur->next==plist){
			printf("%d",cur->data);
		}else{
			printf("%d<->",cur->data);
		}
		cur=cur->next;
	}
	printf("\n");
}
 
void testlist01(){
	Node *plist=listinit();
	listpushback(plist,1);
	listpushback(plist,2);
	listpushback(plist,3);
	listpushback(plist,4);
	listprint(plist);
	
	listpopback(plist);
	listpopback(plist);
	listpopback(plist);
	listpopback(plist);
	listprint(plist);
	
	listpushfront(plist,1);
	listpushfront(plist,2);
	listpushfront(plist,3);
	listpushfront(plist,4);
	listprint(plist);
	
	listpopfront(plist);
	listpopfront(plist);
	listpopfront(plist);
	listpopfront(plist);
	listprint(plist);
}
 
void testlist02(){
	Node *plist=listinit();
	listpushback(plist,1);
	listpushback(plist,1);
	listpushback(plist,1);
	listpushback(plist,1);
	listprint(plist);
	
	Node *pos=listfind(plist,3);
	listinsert(pos,30);
	listprint(plist);
	listerase(pos);
	listprint(plist);
}
 
int main(){
	testlist01();
	testlist02();
}

结果如下：