21. Merge Two Sorted Lists

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
 
        ListNode p1 = l1;
        ListNode p2 = l2;
 
        ListNode fakeHead = new ListNode(0);
        ListNode p = fakeHead;
 
        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 fakeHead.next;
    }
}