HackerHeap

Merge two sorted linked lists and return it as a new sorted list. The new list should be made by splicing together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

Solution 1:

public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
         ListNode p1 = l1;
        ListNode p2 = l2;
 
        ListNode returnNode = new ListNode(0);
        ListNode p = returnNode;
 
        while(p1 != null && p2 != null){
          if(p1.val <= p2.val){
              p.next = p1;
              p1 = p1.next;
          }else{
              p.next = p2;
              p2 = p2.next;
          }
 
          p = p.next;
        }
 
        if(p1 != null)
            p.next = p1;
        if(p2 != null)
            p.next = p2;
 
        return returnNode.next;
    }
}