merge-two-sorted-list.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}
 */

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

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

  while (list1 && list2) {
    if (list1.val <= list2.val) {
      prev.next = list1;
      prev = list1; //
      list1 = list1.next; // Essa linha avança o ponteiro da lista no while
    } else {
      prev.next = list2;
      prev = list2;
      list2 = list2.next;
    }
  }

  if (!list1) prev.next = list2;
  if (!list2) prev.next = list1;

  return dummy.next;
};

const node1 = new ListNode(1, new ListNode(2, new ListNode(4)));
const node2 = new ListNode(2, new ListNode(3, new ListNode(4)));

mergeTwoLists(node1, node2);