114. Flatten Binary Tree to Linked List

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