LeetCode: 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.

源代码:

/**
* 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) {
if (l1 == NULL) return l2;
if (l2 == NULL) return l1;

struct ListNode* head = new ListNode(0);
struct ListNode* tmp = head;
while(l1 != NULL && l2 != NULL){

if (l1->val > l2->val) {
tmp->next = l2;
l2 = l2->next;
}
else {
tmp->next = l1;
l1 = l1->next;
}
tmp = tmp->next;
}
if (l1 != NULL) tmp->next = l1;
if (l2 != NULL) tmp->next = l2;

return head->next;

}
};