单链表的基本操作

单链表的操作有两种，一种是带头节点的链表，一种是不带头节点的链表：

　　首先我们看一下不带头节点的链表的基本操作：

/****************************************
本程序所写的链表均是不带头节点的链表操作
****************************************/

#include "stdio.h"
#include "stdlib.h"

typedef struct _Node
{
	int data;
	struct _Node* next;
}Node;

Node* InitNode(int val)
{
	Node* NodeFirst = (Node *)malloc(sizeof(Node));
	NodeFirst->data = val;
	NodeFirst->next = NULL;
	
	return NodeFirst;
}

int SqlistDisplay(Node* head)
{
	Node* TmpNode = head;

	if (head == NULL)
	{
		return 1;
	}

	while (1)
	{
		printf("%d", TmpNode->data);
		if (TmpNode->next == NULL)
		{
			break;
		}
		else
		{
			TmpNode = TmpNode->next;
			printf("->");
		}
	}
	printf("
");
	return 0;
}

/**************************
头插法，对链表追加一个结点
***************************/

Node* SqlistHeadInsert(Node* head, int val)
{
	Node* NodeInsert = NULL;

	if (head == NULL)
	{
		return head;
	}

	NodeInsert = (Node*)malloc(sizeof(Node));

	NodeInsert->data = val;
	NodeInsert->next = head;

	return NodeInsert;
}

/*****************************
头插法，对链表末尾追加一个结点
*****************************/

Node* SqlistTailInsert(Node* head, int val)
{
	Node* NodeInsert = NULL;
	Node* TmpNode = head;

	if (head == NULL)
	{
		return head;
	}

	NodeInsert = (Node*)malloc(sizeof(Node));

	NodeInsert->data = val;
	NodeInsert->next = NULL;
	while (TmpNode->next != NULL)
	{
		TmpNode = TmpNode->next;
	}

	TmpNode->next = NodeInsert;

	return head;
}

/*****************************
添加操作，在指定位置添加结点
*****************************/

Node* NodeInsert(Node* head, int location, int val)
{
	Node* TmpNode = NULL;
	Node* InsertNode = NULL;

	if (head == NULL || location == 0)
	{
		InsertNode = (Node*)malloc(sizeof(Node));
		InsertNode->data = val;
		InsertNode->next = head;
		return InsertNode;
	}
	else
	{
		TmpNode = head;
		while(--location)
		{
			TmpNode = TmpNode->next;
			if (TmpNode == NULL)
			{
				printf("index has over flow!
");
				return head;
			}
		}

		InsertNode = (Node*)malloc(sizeof(Node));
		InsertNode->data = val;
		InsertNode->next = TmpNode->next;
		TmpNode->next = InsertNode;
		return head;
	}
}

/*****************************
删除操作，删除指定位置的结点
*****************************/

Node* NodeDelete(Node* head, int location)
{
	Node* FinalNode = head;
	Node* TmpNode = head;
	Node* freeNode = NULL;

	if (head == NULL)
	{
		return head;
	}

	if (location == 0)
	{
		FinalNode = head->next;
		free(TmpNode);
	}
	else
	{
		while (--location)
		{
			TmpNode = TmpNode->next;
			if (TmpNode->next == NULL)
			{
				printf("index node does not exist!
");
				return NULL;
			}
		}

		freeNode = TmpNode->next;
		TmpNode->next = freeNode->next;
		free(freeNode);
	}

	return FinalNode;
}

/*****************************
链表的逆序操作，将链表的顺序逆转
*****************************/

Node* ListReserse(Node* head)
{
	if (head == NULL || head->next == NULL)
	{
		return head;
	}

	Node* pre = NULL;
	Node* cur = NULL;
	Node* nex = NULL;

	pre = head;
	cur = pre->next;

	while (cur)
	{
		nex = cur->next;
		cur->next = pre;
		pre = cur;
		cur = nex;
	}

	head->next = NULL;
	head = pre;

	return head;
}

/*****************************
链表的合并操作
*****************************/

Node* ListMerge(Node* L1, Node* L2)
{
	Node* L = NULL;
	Node* r = NULL;
	Node* p1 = L1;
	Node* p2 = L2;

	if (p1->data < p2->data)
	{
		L = p1;
		p1 = p1->next;
	}
	else
	{
		L = p2;
		p2 = p2->next;
	}

	r = L;
	while (p1&&p2)
	{
		if (p1->data < p2->data)
		{
			r->next = p1;
			r = p1;
			p1 = p1->next;
		}
		else
		{
			r->next = p2;
			r = p2;
			p2 = p2->next;
		}
	}

	if (p1)
	{
		r->next = p1;
	}
	else
	{
		r->next = p2;
	}

	return L;
}

int main()
{
	Node* Sqlist = InitNode(1);
	Node* Sqlist1 = InitNode(999);
	Node* SqlistMerged = NULL;

	Sqlist = SqlistTailInsert(Sqlist, 2);
	Sqlist = SqlistTailInsert(Sqlist, 3);
	Sqlist = SqlistTailInsert(Sqlist, 4);
	Sqlist = SqlistTailInsert(Sqlist, 5);

	Sqlist1 = SqlistTailInsert(Sqlist1, 875);
	Sqlist1 = SqlistTailInsert(Sqlist1, 325);
	Sqlist1 = SqlistTailInsert(Sqlist1, 478);
	Sqlist1 = SqlistTailInsert(Sqlist1, 533);

	SqlistDisplay(Sqlist);

	Sqlist = ListReserse(Sqlist);

	SqlistDisplay(Sqlist);

	Sqlist = NodeInsert(Sqlist, 2, 123);

	SqlistDisplay(Sqlist);

	Sqlist = NodeDelete(Sqlist, 4);

	SqlistDisplay(Sqlist);

	SqlistMerged = ListMerge(Sqlist, Sqlist1);
	SqlistDisplay(SqlistMerged);

	getchar();
}