/**
 * 
 * Ashish Patel
 * e: ashishsushilPatel@gmail.com
 * w: https://ashish.me
 *
 */

function ListNode(val) {
  this.val = val;
  this.next = null;
}

function mergeTwoSortedLists(l1, l2) {
  let dummyHead = new ListNode();
  let current = dummyHead;
  while(l1 && l2){
    if(l1.val < l2.val) {
      current.next = l1
      l1 = l1.next
    } else {
      current.next = l2
      l2 = l2.next
    }
    current = current.next
  }
  while(l1) {
    current.next = l1
    l1 = l1.next
    current = current.next
  }

  while(l2) {
    current.next = l2
    l2 = l2.next
    current = current.next
  }
  return dummyHead.next
}

const ll1 = new ListNode(1)
ll1.next = new ListNode(2)
ll1.next.next = new ListNode(4)

const ll2 = new ListNode(1)
ll2.next = new ListNode(3)
ll2.next.next = new ListNode(4)

const ll3 = new ListNode(1)
ll3.next = new ListNode(1)
ll3.next.next = new ListNode(2)
ll3.next.next.next = new ListNode(3)
ll3.next.next.next.next = new ListNode(4)
ll3.next.next.next.next.next = new ListNode(4)

test('merge Two Sorted Lists', () => {
  expect(mergeTwoSortedLists(ll1,ll2)).toEqual(ll3)
});