将两个非递减的有序链表合并为一个非递增的有序链表。
要求结果链表仍使用原来两个链表的存储空间, 不另外占用其它的存储空间。表中允许有重复的数据。
a: 1, 2, 2, 4, 5, 7, 8, 9, 10
b: 1, 2, 3, 6, 7, 8

#include <iostream>
using namespace std;

typedef int Elemtype;
#define ERROR 0;
#define OK    1;

typedef struct LNode
{
	Elemtype data;      //结点保存的数据
	struct LNode* next; //结构体指针
}LNode, * LinkList;

/*单链表初始化*/
bool Init_LinkList(LinkList& L)
{
	L = (LinkList)malloc(sizeof(LNode));  //新建头结点
	if (L == NULL)
	{
		return ERROR;
	}
	L->data = 0;
	L->next = NULL;
	return OK;
}

/*单链表头插法*/
bool LinkList_head_instert(LinkList& L)
{
	int x = 0;
	LNode* p = NULL;
	while (cin >> x)
	{
		p = (LinkList)malloc(sizeof(LNode));
		if (p != NULL)  //防止分配地址失败
		{
			p->data = x;
			p->next = L->next;
			L->next = p;
			if (cin.get() == '\n') break;  //检测换行符
		}
		else
		{
			exit(0);
			cout << "内存分配失败" << endl;
		}
	}
	return OK;
}

/*单链表尾插法*/
bool LinkList_tail_instert(LinkList& L)
{
	int x = 0;
	LNode* p = NULL;
	LNode* r = NULL;
	r = L;
	while (cin >> x)
	{
		p = (LinkList)malloc(sizeof(LNode));
		if (p != NULL)  //防止分配地址失败
		{
			p->data = x;
			p->next = NULL;
			r->next = p;
			r = p;
			if (cin.get() == '\n') break;  //检测换行符
		}
		else
		{
			exit(0);
			cout << "内存分配失败" << endl;
		}
	}
	return OK;
}

/*单链表遍历*/
bool LinkList_All_value(LinkList L)
{
	if (L->next == NULL)
	{
		cout << "链表为空" << endl;
		return ERROR;
	}
	LNode* s = NULL;
	s = L->next;
	while (s != NULL)
	{
		cout << s->data << "   ";
		s = s->next;
	}
	cout << endl;
	free(s);
	return OK;
}

/*单链表长度*/
int LinkList_length(LinkList L)
{
	int count = 0;
	LNode* s = NULL;
	s = L->next;
	while (s != NULL)
	{
		count++;
		s = s->next;
	}
	return count;
}

/*清空单链表*/
void Clear_LinkList(LinkList& L)
{
	LNode* p = L->next;
	LNode* q = NULL;
	while (p != NULL)
	{
		q = p->next;
		free(p);
		p = q;
	}
	L->next = NULL;
}

/*销毁单链表*/
void Destory_LinkList(LinkList& L)
{
	LNode* p = NULL;
	LNode* q = NULL;
	p = L;
	while (p != NULL)
	{
		q = p->next;
		free(p);
		p = q;
	}
	L = NULL;
}

/*将两个非递减的有序链表合并为一个非递增的有序链表。
要求结果链表仍使用原来两个链表的存储空间, 不另外占用其它的存储空间。表中允许有重复的数据。*/
//a: 1, 2, 2, 4, 5, 7, 8, 9, 10
//b: 1, 2, 3, 6, 7, 8

//主要采用头插法
bool hebing(LinkList& La, LinkList& Lb, LinkList& Lc)
{
	LNode* pa = NULL;
	LNode* pb = NULL;
	LNode* q = NULL;
	pa = La->next;
	pb = Lb->next;
	Lc = La;
	Lc->next = NULL;
	if (pa == NULL && pb == NULL)
	{
		cout << "两个单链表都为空!!!" << endl;
		return ERROR;
	}
	while (pa != NULL || pb != NULL)
	{
		if (pa == NULL && pb != NULL)     //单链表La为空
		{
			q = pb->next;
			pb->next = Lc->next;
			Lc->next = pb;
			pb = q;
		}
		else if (pa != NULL && pb == NULL) //单链表Lb为空
		{
			q = pa->next;
			pa->next = Lc->next;
			Lc->next = pa;
			pa = q;
		}
		else  //pa != NULL && pb != NULL
		{
			if (pa->data <= pb->data)
			{
				q = pa->next;
				pa->next = Lc->next;
				Lc->next = pa;
				pa = q;
			}
			else//pa->data > pb->data
			{
				q = pb->next;
				pb->next = Lc->next;
				Lc->next = pb;
				pb = q;
			}
		}
	}
	delete Lb;//删除单链表Lb
	return OK;
}

int	main(void)
{
	LinkList L1 = NULL;
	Init_LinkList(L1);
	LinkList_tail_instert(L1);//1 2 2 4 5 7 8 9 10
	LinkList_All_value(L1);
	LinkList L2 = NULL;
	Init_LinkList(L2);
	LinkList_tail_instert(L2);//1 2 3 6 7 8
	LinkList_All_value(L2);
	LinkList L3 = NULL;
	hebing(L1, L2, L3);
	LinkList_All_value(L3);
	return 0;
}