leetcode：Merge Two Sorted Lists （链接两个有序链表）【面试算法题】

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.

题意链接两个有序链表。

没啥难点，注意头指针的建立和空指针。

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
ListNode *root,*p;
root=new ListNode(-1);
p=root;
while(1)
{
if(l1==NULL){p->next=l2;break;}
if(l2==NULL){p->next=l1;break;}
if(l1->val<l2->val)
{
p->next=l1;
l1=l1->next;
}
else
{
p->next=l2;
l2=l2->next;
}
p=p->next;
}
ListNode *temp=root->next;
delete(root);
return temp;
}
};
//http://blog.csdn.net/havenoidea