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.
2つの秩序チェーンテーブルを新しい秩序チェーンテーブルに合成します.

/**
 * 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 || l2==NULL)
            return l1==NULL ? l2 : l1;
            
        ListNode *head, *curr;
        
        l1->val <= l2->val ? (head=l1, l1=l1->next) : (head=l2, l2=l2->next);
        curr = head;
        
        while (l1!=NULL && l2!=NULL) {
            if (l1->val <= l2->val) {
                curr->next = l1;
                curr = curr->next;
                l1 = l1->next;   
            } else {
                curr->next = l2;
                curr = curr->next;
                l2 = l2->next;
            }
        }
        
        if (l1 != NULL)
            curr->next = l1;
        
        if (l2 != NULL)
            curr->next = l2;
        
        return head;
    }
};