LeetCode#21 Merge Two Sorted Lists

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：就是给你两个已经排好序的链表，然后叫你合并成一个链表。
思路：就是考链表的操作。代码：

/**
 * 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 *t1=l1;
        ListNode *t2=l2;
        ListNode *head=new ListNode(0);      //new的应用很巧妙  不用再malloc了
        ListNode *temp=head;
        while(t1!=NULL||t2!=NULL)
        {
            while((t2==NULL&&t1!=NULL)||(t1!=NULL&&t1->val<=t2->val))
            {
                temp->next=t1;
                temp=temp->next;
                t1=t1->next;
            }
            while((t1==NULL&&t2!=NULL)||(t2!=NULL&&t1->val>t2->val))
            {
                temp->next=t2;
                temp=temp->next;
                t2=t2->next;
            }
        }
        temp->next=NULL;
        return head->next;
    }
};