【LeetCode OJ】Merge Two Sorted Lists

题目：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.

struct ListNode {
	int val;
	ListNode *next;
	ListNode(int x) : val(x), next(NULL) {}
	
};
ListNode *mergeTwoLists(ListNode *l1, ListNode *l2)
{
	if (l2 == NULL)
		return l1;
	if (l1 == NULL)
		return l2;
	ListNode  *r, *head;
	head = NULL;
	if (l1->val <= l2->val)  //哪个链表的第一个节点小就把头指针指向哪个节点
	{
		head = l1;
		l1 = l1->next;
	}
	else
	{
		head = l2;
		l2 = l2->next;
	}
	r = head;
	while (l1&&l2)    //比较大小
	{
		if (l1->val <= l2->val)
		{
			r->next = l1;
			l1 = l1->next;
		}
		else
		{
			r->next = l2;
			l2 = l2->next;
		}
		r = r->next;
	}
	if (l1 == NULL)   //l1为空，直接连接l2
	{
		r->next = l2;
	}
	if (l2 == NULL)  //l2为空，直接连接l1
	{
		r->next = l1;
	}
	return head;
}

【LeetCode OJ】Merge Two Sorted Lists

原文：http://blog.csdn.net/xujian_2014/article/details/44802159