有序链表合并

有序链表合并

#include<stdio.h>
#include<iostream>
using namespace std;
//测试数据
const int arrrlens = 5;
int arr_1[arrrlens] = { 9, 7, 5, 3, 1 };
int arr_2[arrrlens] = { 0, 2, 4, 6, 8 };
class Node {
public:
	//构造函数，创建一个节点
	Node(int el = NULL, Node* ptr = NULL) {
		infor = el;
		next = ptr;
	}
	int infor;
	Node* next;
};
class NodeList {
public:
	NodeList() {
		head = new Node();
	}
	~NodeList() {
		delete head;
	}
	//节点插入头部
	void printList();
	void addToHead();
	void addToTail();
	Node* getHead();
	//Node* mergeTwoOrderLists(NodeList*, NodeList*);
	
private:
	Node* head;
};
//头部插入法链表顺序与输入数据顺序相反
Node* NodeList::getHead()
{
	return head;
}
void NodeList::addToHead()
{
	 
	for (int i = 0; i < arrrlens; i++)
	{
		int node = arr_1[i];
		Node* p = new Node(node, NULL);
		if (i == 0) {
			head = p;
		}
		else {
			p->next = head;
			head = p;
		}
	}
}
void NodeList::addToTail()
{ 
	Node *fp = head;
	for (int i = 0; i < arrrlens; i++)
	{
		int node = arr_2[i];
		Node* p = new Node(node, NULL);
		fp->next = p;
		fp = p;
	}
	//删除头部为空节点
	Node* newHead = head->next;
	delete head;
	head = newHead;
}
//非递归合并
Node* mergeTwoOrderLists(Node* pHead1, Node* pHead2)
{
	Node* newHead = NULL;
	Node* pTail = NULL;
	if (pHead1 == NULL) {
		return pHead2;
	}
	else if (pHead2 == NULL) {
		return pHead1;
	}
	else {
		//确定头指针,newHead用来索引后面的节点
		if (pHead1->infor < pHead2->infor) {
			newHead = pHead1;
			pHead1 = pHead1->next;
		}else {
			newHead = pHead2;
			pHead2 = pHead2->next;
		}
		//pTail一直next直到结束
		pTail = newHead;
		while (pHead1 && pHead2)
		{
			if (pHead1->infor < pHead2->infor) {
				pTail->next = pHead1;
				pHead1 = pHead1->next;
			}
			else {
				pTail->next = pHead2;
				pHead2 = pHead2->next;
			}
			pTail = pTail->next;
		}
		if (pHead1 == NULL) {
			pTail->next = pHead2;
		}
		else if (pHead2 == NULL) {
			pTail->next = pHead1;
		}
	}
	return newHead;
	return NULL;
}
//递归合并有序链表
Node* __mergeTwoOrderLists(Node* pHead1, Node* pHead2)
{
	Node* newHead = NULL;
	if (pHead1 == NULL) {
		return pHead2;
	}
	else if (pHead2 == NULL) {
		return pHead1;
	}
	if (pHead1->infor < pHead2->infor)
	{
		newHead = pHead1;
		newHead->next = __mergeTwoOrderLists(pHead1->next, pHead2);
	}else {
		newHead = pHead2;
		newHead->next = __mergeTwoOrderLists(pHead1, pHead2->next);
	}
	return newHead;
}

void NodeList::printList()
{
	Node* p = head;
	while (p != NULL)
	{
		printf("%d ", p->infor);
		p = p->next;
	}
	printf("\n");
}

int main()
{
	NodeList nlist_1, nlist_2;
	nlist_1.addToHead();
	nlist_2.addToTail();
	nlist_1.printList();
	nlist_2.printList();
	//Node* newHead = mergeTwoOrderLists(nlist_1.getHead(), nlist_2.getHead());
	Node* newHead = __mergeTwoOrderLists(nlist_1.getHead(), nlist_2.getHead());
	while (newHead != NULL)
	{
		printf("%d ", newHead->infor);
		newHead = newHead->next;
	}
	printf("\n");
}

结果：