数据结构学习第五课（双向链表）

2，双向链表

2.1双向链表基本框架

typedef int Data;
typedef struct _Node
{
	Data data;//数据域
	struct _Node* next;//后继指针--指向下一个结点
	struct _Node* prev;//前驱指针--指向上一个结点
}Node;//结点
typedef struct DoubleList
{
	int size;//当前结点数量
	Node* front;//指向头结点的指针
	Node* tail;//指向尾结点的指针
}DuList;//双向链表

2.2创建一个双向链表

DuList* createDuList()
{
	DuList* list = calloc(1, sizeof(DuList));
	assert(list != NULL);
	//创建头结点
	list->front = calloc(1, sizeof(Node));
	assert(list->front != NULL);
	list->tail = list->front;//让头指针和尾指针都指向头结点
	return list;
}

2.3创建一个结点

//创建一个结点
Node* createNode(Data data)
{
	Node* newNode = calloc(1, sizeof(Node));
	if (newNode==NULL)
	{
		return NULL;
	}
	newNode->data = data;
	return newNode;
}

2.4尾插

//尾插
void push_back(DuList* list, Data data)
{
	Node* newNode = createNode(data);
	newNode->next = list->tail->next;//新结点的后继指针指向NULL
	newNode->prev = list->tail;//新结点的前驱指针指向原先的最后一个
	list->tail->next = newNode;//让原先的尾结点指向新结点
	list->tail = newNode;//让尾指针指向新结点
	list->size++;
}

2.5头插

//头插
void push_front(DuList* list, Data data)
{
	Node* newNode = createNode(data);
	newNode->next = list->front->next;
	newNode->prev = list->front;
	list->front->next = newNode;
	list->size++;
}

2.6查看

//输出
void show_list(DuList* list)
{
	if (empty(list))
	{
		return;
	}
	Node* curNode = list->front->next;
	while (curNode!=NULL)
	{
		printf("%d ", curNode->data);
		curNode = curNode->next;
	}
	printf("\n");
}

2.7判断链表是否为空

//判断链表是否为空
#include<stdbool.h>
bool empty(DuList* list)
{
	return list->size == 0;
}

2.8查找指定元素

//查找指定元素，找到返回结点所在的位置，没有则放回NULL
Node* find(DuList* list, Data data)
{
	if (empty(list))
	{
		return NULL;
	}
	Node* curNode = list->front->next;
	while (curNode!=NULL)
	{
		if (curNode->data==data)
		{
			return curNode;
		}
		curNode = curNode->next;
	}
	return NULL;
}

2.9插入

//插入
void insert(DuList* list, Node* iterator, Data data)
{
	Node* newNode = createNode(data);
	Node* prevNode = iterator->prev;//保存要插入的位置的上一个结点

	newNode->next = iterator;//让新结点连上去
	newNode->prev = prevNode;
	
	iterator->prev = newNode;//让前后结点连上新结点
	prevNode->next = newNode;
	
	list->size++;
}

2.10尾部删除

//尾部删除
void pop_back(DuList* list)
{
	if (empty(list))
	{
		return;
	}
	list->tail = list->tail->prev;//让尾指针前移一位
	free(list->tail->next);
	list->tail->next = NULL;
	list->size--;
}

2.11头部删除

//头部删除
void pop_front(DuList* list)
{
	if (empty(list))
	{
		return;
	}
	Node* delNode = list->front->next;//保存删除的结点
	list->front->next = delNode->next;
	//判断是不是只有一个结点，如果只有一个结点，需要对尾结点进行处理
	if (delNode->next!=NULL)
	{
		delNode->next->prev = list->front;
	}
	else
	{
		list->tail = list->front;
	}
	free(delNode);
	list->size--;
}

2.12指定元素删除

//指定元素删除
void erase_val(DuList* list, Data data)
{
	Node* delNode = find(list, data);
	if (delNode==NULL)
	{
		return;
	}
	Node* prevNode = delNode->prev;//保存上一个结点
	prevNode->next = delNode->next;
	delNode->next->prev = prevNode;
	free(delNode);
	list->size--;
}

2.13排序

//排序
void sort(DuList* list)
{
	if (empty(list))
	{
		return;
	}
	for (Node* i = list->front->next; i->next!= NULL; i=i->next)
	{
		for (Node* k = list->front->next; k->next != NULL; k = k->next)
		{
			if (k->data>k->next->data)
			{
				Data t = k->data;
				k->data = k->next->data;
				k->next->data = t;
			}
		}
	}
}

2.14清除

//清除
void clear(DuList* list)
{
	if (empty(list))
	{
		return;
	}
	while (list->front->next!=NULL)
	{
		pop_front(list);
	}
	list->size = 0;
}

2.15销毁

//销毁
void destory(DuList** list)
{
	clear(*list);
	free((*list)->front);
	free(*list);
	*list = NULL;
}

2.16反转

//反转
void reverse(DuList* list)
{
	if (size(list) <= 1)
	{
		return;
	}
	Node* curNode = list->front->next;
	Node* prevNode = NULL;
	Node* nextNode = NULL;
	list->tail = curNode;
	while (curNode!=NULL)
	{
		nextNode = curNode->next;
		curNode->next = prevNode;
		curNode->prev = nextNode;
		prevNode = curNode;
		curNode = nextNode;//移动当前指针
	}
	list->front->next = prevNode;
	prevNode->prev = list->front;
}

2.17求大小

int size(DuList* list)
{
	return list->size;
}