0021.Merge Two Sorted Lists

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.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

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/**
 * 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* l = new ListNode(0);
        ListNode* tmp = l;
        while(l1 && l2){
            if(l1->val > l2->val){
                tmp->next = l2;
                l2 = l2->next;
            }
            else{
                tmp->next = l1;
                l1 = l1->next;
            }
            tmp = tmp->next;
        }
        if(!l1) tmp->next = l2;
        else tmp->next = l1;
        return l->next;
    }
};