Flatten Binary Tree to Linked List

 1 public class Solution {
 2     public void flatten(TreeNode root) {
 3         if(root==null) return;
 4         if(root.left!=null){
 5             TreeNode left = root.left;
 6             TreeNode right = root.right;
 7             root.left = null;
 8             root.right = left;
 9             TreeNode p = left;
10             while(p.right!=null){
11                 p = p.right;
12             }
13             p.right = right;
14         }
15         flatten(root.right);
16     }
17 }