数据结构-链表篇

链表的优点：

1. 插入和删除速度快
2. 内存利用率高
3. 可以随时扩展，不必担心存储满

链表的缺点：

1. 不能随机查找，只能通过从头一个一个找，查找效率低

实现如下：

#include <stdio.h>
#include <malloc.h>

typedef struct Node
{
	int data;            //数据域
	struct Node *pNext;  //指针域，存储下一个节点的地址
}Node;

//函数声明
Node* head_create_list();  //头插法创建链表
Node* end_create_list();   //尾插法创建链表
void insert(Node *phead, int address, int val);  //插入节点
void removes(Node *phead, int address, int *removeItem);  //删除节点
void sort(Node *phead);   //排序
void show(Node *head);  //输出链表的所有元素
int number(Node *head);  //判断链表里面元素的个数


void main()
{
	int choose;
	int address, val, removeItem;
	Node *phead = NULL;      //声明头指针，指向头节点
	while(1)
	{
		printf("为链表提供以下功能选项:\n");
		printf("1. 使用头插法建立链表\n");
		printf("2. 使用尾插法建立链表\n");
		printf("3. 插入元素\n");
		printf("4. 删除元素\n");
		printf("5. 排序\n");
		printf("6. 输出所有元素\n");
		printf("请输入选项(输入0退出): ");
		scanf("%d", &choose);
		switch(choose)
		{
			case 1:
				phead = head_create_list();
				break;
			case 2:
				phead = end_create_list();
				break;
			case 3:
				printf("请输入要插入的位置: ");
				scanf("%d", &address);
				printf("请输入要插入的元素: ");
				scanf("%d", &val);
				insert(phead, address, val);
				printf("插入成功!!\n\n");
				break;
			case 4:
				printf("请输入要删除的位置: ");
				scanf("%d", &address);
				removes(phead, address, &removeItem);
				printf("删除成功, 删除的元素为%d\n\n", removeItem);
				break;
			case 5:
				printf("正在排序中...\n");
				sort(phead);
				break;
			case 6:
				show(phead);
				break;
			default:
				exit(-1);
		}
	}
}

//头插法
Node* head_create_list()
{
	int i, size, val;
	Node *phead = (Node*)malloc(sizeof(Node));    //为头节点分配空间
	phead->pNext = NULL;
	printf("请输入元素的个数:");
	scanf("%d", &size);
	if(size <= 0)
	{
		printf("值无效!\n\n");
		free(phead);
		return NULL;
	}
	for(i=1; i<=size; i++)
	{
		Node *pnew = (Node*)malloc(sizeof(Node));
		printf("输入第%d个节点的值: ", i);
		scanf("%d", &val);
		if(pnew == NULL)
		{
			printf("分配空间失败!");
			exit(-1);
		}
		pnew->data = val;
		pnew->pNext = phead->pNext;
		phead->pNext = pnew;
	}
	printf("头插法链表建立成功!\n\n");
	return phead;
}

//尾插法
Node* end_create_list()
{
	int i, size, val;
	Node *phead = (Node*)malloc(sizeof(Node));
	Node *p = phead;        //声明一个指针，用来指向最末尾的节点
	phead->pNext = NULL;
	printf("请输入元素的个数:");
	scanf("%d", &size);
	if(size <= 0)
	{
		printf("值无效!\n\n");
		free(phead);
		return NULL;
	}
	for(i=1; i<=size; i++)
	{
		Node *pnew = (Node*)malloc(sizeof(Node));
		printf("请输入第%d个节点的值: ", i);
		scanf("%d", &val);
		if(pnew == NULL)
		{
			printf("分配空间失败!");
			exit(-1);
		}
		pnew->data = val;
		p->pNext = pnew;
		pnew->pNext = NULL;
		p = pnew;
	}
	printf("尾插法链表建立成功!\n\n");
	return phead;
}

//插入节点
void insert(Node *phead, int address, int val)
{
	Node *p = phead;
	Node *pnew = (Node*)malloc(sizeof(Node));
	int i;
	if(address>number(phead)+1 || address<=0)
	{
		printf("不在范围内!\n\n");
		return;
	}
	else
	{
		for(i=0; i<address-1; i++)
		{
			p = p->pNext;
		}
		pnew->data = val;
		pnew->pNext = p->pNext;
		p->pNext = pnew;
	}
}

//删除节点
void removes(Node *phead, int address, int *removeItem)
{
	int i;
	Node *p1, *p2;
	p1 = phead;
	p2 = phead;
	if(number(phead) == 0)
	{
		printf("链表无元素!\n\n");
		return;
	}
	else if(address>number(phead) || address <=0)
	{
		printf("不在范围内!\n\n");
		return;
	}
	for(i=0; i<address; i++)
	{
		if(i == address-1)
		{
			p2 = p2->pNext;
		}
		else
		{
			p1 = p1->pNext;
			p2 = p2->pNext;
		}
	}
	p1->pNext = p2->pNext;
	p2->pNext = NULL;
	*removeItem = p2->data;
	free(p2);
}

//排序
void sort(Node *phead)
{
	if(number(phead) == 0)
	{
		printf("链表无元素!\n\n");
		return;
	}
	else
	{
		Node *p = phead;
		Node *p1;
		int i, j;
		int temp;
		int all = number(phead);
		for(i=0,p=p->pNext; i<all-1; i++,p=p->pNext)
		{
			for(j=i+1,p1=p->pNext; j<all; j++,p1=p1->pNext)
			{
				if(p->data > p1->data)
				{
					temp = p->data;
					p->data = p1->data;
					p1->data = temp;
				}
			}
		}
		printf("排序成功!\n\n");
	}
}

//输出链表的所有元素
void show(Node *phead)
{
	Node *p = phead;
	if(p == NULL)
	{
		printf("链表无元素!\n\n");
		return;
	}
	else
	{
		while(p->pNext != NULL)
		{
			printf("%d ",p->pNext->data);
			p = p->pNext;
		}
		printf("\n\n");
	}

}

//返回当前链表中节点的个数
int number(Node *phead)
{
	Node *p = phead;
	int num = 0;
	if(phead == NULL)
	{
		return 0;
	}
	while(p->pNext != NULL)
	{
		num++;
		p = p->pNext;
	}
	return num;
}