双向链表

标签：双向链表

引言：

        单链表存在一个问题，当我们想要访问某个结点的前一个结点时，要从头结点开始访问。显然这样的操作是令人烦躁的。为此，双向链表出现，它比单链表多出了一个指针域，指向前一个结点。这样，对于双向链表，就可以方便的从后向前遍历链表了。但多出的问题是对于插入和删除结点的开销要增加一倍。

分析描述：

        双向链表存储结构图为：，用结构体表示如下：

typedef	int	ElemType;
typedef struct LNode{
	ElemType	data;
	struct LNode *prior;
	struct LNode *next;
}LNode, *PLNode;

PLNode InitDList(void)
{
	PLNode HeadLNode = (PLNode)malloc(sizeof(LNode));
	if(HeadLNode == NULL){
		printf("malloc memory fail.\n");	
		return NULL;
	}

	HeadLNode->prior = HeadLNode->next = HeadLNode;

	return HeadLNode;
}

PLNode CreateDList(PLNode PHeadNode)
{
	PLNode TmpLNode = (PLNode)malloc(sizeof(LNode));
	if(TmpLNode == NULL){
		printf("malloc memory fail.\n");	
		return PHeadNode;
	}
	TmpLNode->next = NULL;

	while(scanf("%d", &TmpLNode->data) != 0){
		TmpLNode->next        = PHeadNode->next;
		TmpLNode->prior       = PHeadNode;
		PHeadNode->next       = TmpLNode;
		if(TmpLNode->next != NULL)//此处的判断是针对空链表的操作，如果是空链表，下面的语句就不做。
			TmpLNode->next->prior = TmpLNode;	

		TmpLNode = (PLNode)malloc(sizeof(LNode));
		if(TmpLNode == NULL){
			return PHeadNode;
		}
	}
	free(TmpLNode);

	return PHeadNode;
}

void TraverseDList(PLNode PHeadNode)
{
	PLNode TmpLNode = PHeadNode;

	if(PHeadNode == NULL) {
		printf("input element faulse.\n");
		return ;
	}

	while(TmpLNode->next != NULL){
		printf("%d ", TmpLNode->next->data);	
		TmpLNode = TmpLNode->next;
	}
	putchar('\n');
}

int ListLength(PLNode PHeadNode)
{
	int count = 0;
	while(PHeadNode->next != NULL){
		count++;
		PHeadNode = PHeadNode->next;	
	}

	return count;
}

PLNode InsertDList(PLNode PHeadNode, ElemType data, int Index)
{
	int index = 0;
	PLNode TmpLNode = PHeadNode;

	if(PHeadNode == NULL || Index < 0 || Index > ListLength(PHeadNode) + 1){
		printf("input element faulse.\n");	
		return NULL;
	}

	for(index = 1; index < Index; index++){
		TmpLNode = TmpLNode->next;	
	}

	PLNode Tmp = (PLNode)malloc(sizeof(LNode));
	if(Tmp == NULL){
		printf("malloc memory faluse.\n");	
		return PHeadNode;
	}
	Tmp->data = data;

	Tmp->next = TmpLNode->next;
	Tmp->prior = TmpLNode->prior;
	TmpLNode->next = Tmp;
	TmpLNode->prior = Tmp;

	return PHeadNode;
}

PLNode DeleteList(PLNode PHeadNode,  int Index)
{
	int index;
	PLNode TmpNode = PHeadNode;

	if(PHeadNode == NULL || Index < 0 || Index > ListLength(PHeadNode)){
		printf("input element faulse.\n");	
		return NULL;
	}
	

	for(index = 0; index < Index; index++){
		TmpNode = TmpNode->next;	
	}
	TmpNode->prior->next = TmpNode->next;
	if(TmpNode->next != NULL)
		TmpNode->next->prior = TmpNode->prior;
	free(TmpNode);

	return PHeadNode;
}

PLNode DeleteList(PLNode PHeadNode,  int Index)
{
	int index;
	PLNode TmpNode = PHeadNode;

	if(PHeadNode == NULL || Index <= 0 || Index > ListLength(PHeadNode)){
		printf("input element faulse.\n");	
		return NULL;
	}
	
	for(index = 0; index < Index; index++){
		TmpNode = TmpNode->next;	
	}

	TmpNode->prior->next = TmpNode->next;
	TmpNode->next->prior = TmpNode->prior;

	free(TmpNode);

	return PHeadNode;
}

双向链表,布布扣,bubuko.com

双向链表

标签：双向链表

原文地址：http://blog.csdn.net/to_be_it_1/article/details/37570681