LeetCode Merge Two Sorted Lists C++

#include <iostream>
#include <vector>
#include<algorithm>
#include <queue>
using namespace std;

/************************************************************************/
/*
Problem:
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

For example,

Given linked list: 1->2->3->4->5,
Given linked list: 2->3->4->5->6;

output:
1-2-2-3-3-4-4-5-5-6; linklist ;
Note:

Author  :   crazys_popcorn@126.com

DateTime:   2017年8月10日 13:16:07

*/
/************************************************************************/

struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2)
{

if (l1 == NULL && l2 == NULL)
return NULL;
ListNode *newlist = new ListNode(0);
ListNode *head = newlist;

while (l1 != NULL ||l2 !=NULL)
{

if (l2 == NULL || l1 == NULL)
{

if (l1 == NULL)
{
head->next = l2;
head = head->next;
l2 = l2->next;
}
else
{
head->next = l1;
head = head->next;
l1 = l1->next;

}
continue;
}

if (l1->val > l2->val)
{
head->next = l2;
head = head->next;
l2 = l2->next;
}
else if (l1->val < l2->val)
{

head->next = l1;
head = head->next;
l1 = l1->next;
}
else
{
head->next = l2;
head = head->next;
l2 = l2->next;
}

}
return newlist->next;

}
};

void main()
{

ListNode *t1 = new ListNode(0);
ListNode *t2 = new ListNode(0);
ListNode *t3 = new ListNode(0);
ListNode *t4 = new ListNode(0);
t1->val = 4;
t2->val = 4;
t3->val = 4;
t4->val = 5;
t1->next = t2;
t2->next = t3;
t3->next = t4;
ListNode *tt1 = new ListNode(0);
ListNode *tt2 = new ListNode(0);
ListNode *tt3 = new ListNode(0);
ListNode *tt4 = new ListNode(0);
tt1->val = 1;
tt2->val = 2;
tt3->val = 3;
tt4->val = 4;
tt1->next = tt2;
tt2->next = tt3;
tt3->next = tt4;
Solution s1;
ListNode  *temp = s1.mergeTwoLists(t1, tt1);

system("pause");
return ;
}