Java for Leetcode Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

         1        /        2   5      /\        3   4   6

The flattened tree should look like:

   1         2             3                 4                     5                         6
Problem Solving Ideas:
Trying to sort through the new TreeNode is not possible, and the meaning of this question is to prune the existing tree. The Java implementation is as follows:

    static public void Flatten (TreeNode root) {while    (root!=null) {            if (root.left!=null) {                  TreeNode pre = Root.left;                  while (pre.right!=null)                      pre = Pre.right;                  Pre.right = root.right;                  Root.right = Root.left;                  Root.left = null;              }              root = Root.right;          }     }

Java for Leetcode Flatten Binary Tree to Linked List