021. Merge Two Sorted Lists.cpp

/**
* 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 || !l2) return l1 ? l1 : l2;
		ListNode head(0);
		ListNode* cur = &head;
		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 head.next;
	}
};