LeetCode | Merge Two Sorted Lists

https://leetcode.com/problems/merge-two-sorted-lists/

模拟归并排序中的归并操作。由于链表的灵活性，可以实现O(1)的空间复杂度。

C++

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode dummy(0);
        ListNode *cur = &dummy;
        while (l1 && l2) {
            if (l1->val < l2->val) {
                cur->next = l1;
                l1 = l1->next;
            } else {
                cur->next = l2;
                l2 = l2->next;
            }
            cur = cur->next;
        }
        cur->next = l1 ? l1 : l2;
        return dummy.next;
    }
};