Day 9 Interview

Key to solve this problem

chcreate new linked list, and how to return the head of the linked list (the first linked node)

The key to solve the problem is defining a fake head. Then compare the first elements from each list. Add the smaller one to the merged list. Finally, when one of them is empty, simply append it to the merged list, since it is already sorted.

Java Solution

 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
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){
     = p1;
              p1 =;
     = p2;
              p2 =;
          p =;
        if(p1 != null)
   = p1;
        if(p2 != null)
   = p2;

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s