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.

分析：

题目的意思将将两个已排序的链表合并成一个链表

定义一个链表头指针和连接指针。连接指针用来连接头指针和较小的元素。

/**
* 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 result(1);
ListNode *l=&result;
while(l1!=NULL&&l2!=NULL){
if(l1->val<l2->val){
l->next=l1;
l1=l1->next;
l=l->next;
}else{
l->next=l2;
l2=l2->next;
l=l->next;
} a
}
while(l1!=NULL&&l2==NULL){
l->next=l1;
l1=l1->next;
l=l->next;
}
while(l2!=NULL&&l1==NULL){
l->next=l2;
l2=l2->next;
l=l->next;
}
return result.next;
}
};