merge-two-sorted-lists.js

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

var mergeTwoLists = function (list1, list2) {
	const dummy = new ListNode(-Infinity);
	let prev = dummy;

	while (list1 && list2) {
		if (list1.val <= list2.val) {
			prev.next = list1;
			prev = list1;
			list1 = list1.next;
		} else {
			prev.next = list2;
			prev = list2;
			list2 = list2.next;
		}
	}
	if (!list1) prev.next = list2;
	if (!list2) prev.next = list1;

	return dummy.next;
};