merge-two-sorted.list.ts

//You are given the heads of two sorted linked lists list1 and list2.

//Merge the two lists into one sorted list. The list should be made by splicing together the nodes of the first two lists.

//Return the head of the merged linked list.

// Input: list1 = [1,2,4], list2 = [1,3,4]
// Output: [1,1,2,3,4,4]
// Example 2:

// Input: list1 = [], list2 = []
// Output: []
// Example 3:

// Input: list1 = [], list2 = [0]
// Output: [0]


//Constraints:

//The number of nodes in both lists is in the range [0, 50].
//-100 <= Node.val <= 100
//Both list1 and list2 are sorted in non-decreasing order.
 

class ListNode {
  val: number;
  next: ListNode | null;
  constructor(val?: number, next?: ListNode | null) {
    this.val = val === undefined ? 0 : val;
    this.next = next === undefined ? null : next;
  }
}

function checker(listNode: ListNode | null): any {
  if (listNode === null) {
    return null;
  }

  let collect = [listNode.val].concat(checker(listNode.next));

  collect.forEach((node) => {
    if (node <= -100 || node >= 100) {
      throw new Error(" range error");
    }
  });
}

function mergeTwoLists(
  list1: ListNode | null,
  list2: ListNode | null
): ListNode | null {
  const result = new ListNode();
  let current = result;

  while (list1 !== null || list2 !== null) {
    if (list1 && list2) {
      current.next = new ListNode(Math.min(list1.val, list2.val));

      current = current.next;

      if (list1.val < list2.val) {
        list1 = list1.next;
      } else {
        list2 = list2.next;
      }
    } else if (list1) {
      current.next = new ListNode(list1.val);
      current = current.next;
      list1 = list1.next;
    } else if (list2) {
      current.next = new ListNode(list2.val);
      current = current.next;
      list2 = list2.next;
    }
  }
  return result.next;
}