content: package codingquestions.leetcode;
  
  /*
  21. Merge Two Sorted Lists
  Solved
  Easy
  Topics
  premium lock icon
  Companies
  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.
  
   
  
  Example 1:
  
  
  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.
  */
  
  import codingquestions.leetcode.ds.ListNode;
  
  /**
   * Definition for singly-linked list.
   * public class ListNode {
   * int val;
   * ListNode next;
   * ListNode() {}
   * ListNode(int val) { this.val = val; }
   * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
   * }
   */
  public class MergeTwoSortedLists {
      public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
          ListNode res = new ListNode();
          ListNode head = res;
          while (list1 != null && list2 != null) {
              if (list1.val < list2.val) {
                  res.next = new ListNode(list1.val);
                  res = res.next;
                  list1 = list1.next;
              } else {
                  res.next = new ListNode(list2.val);
                  res = res.next;
                  list2 = list2.next;
              }
          }
          while (list1 != null) {
              res.next = new ListNode(list1.val);
              res = res.next;
              list1 = list1.next;
          }
          while (list2 != null) {
              res.next = new ListNode(list2.val);
              res = res.next;
              list2 = list2.next;
          }
          head = head.next;
          return head;
      }
  }
  