merge-two-sorted-lists.js

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */

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

function ListNode(val, next) {
  this.val = val === undefined ? 0 : val;
  this.next = next === undefined ? null : next;
}

var mergeTwoLists = function (list1, list2) {
  const list3 = new ListNode();
  let prev = list3;
  while (list1 !== null && list2 !== null) {
    if (list1.val < list2.val) {
      prev.next = list1;
      list1 = list1.next;
    } else {
      prev.next = list2;
      list2 = list2.next;
    }
    prev = prev.next;
  }
  if (list1 === null) {
    prev.next = list2;
  } else {
    prev.next = list1;
  }
  return list3.next;
};

// create first linked list: 1 -> 3 -> 10
var n3 = new ListNode(10, null);
var n2 = new ListNode(3, n3);
var n1 = new ListNode(1, n2);
var L1 = n1;

// create second linked list: 5 -> 6 -> 9
var n6 = new ListNode(9, null);
var n5 = new ListNode(6, n6);
var n4 = new ListNode(5, n5);
var L2 = n4;

mergeTwoLists(L1, L2);