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

 

这道题就是将数变为只有右节点的树。

递归，不是很难。

递归的时候求出左节点的最右孩子即可。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public void flatten(TreeNode root) {
        if( root == null)
            return ;
        else if( root.left == null )
            flatten(root.right);
        else{
            TreeNode node = root.right;
            TreeNode node2 = getRight(root.left);
            root.right = root.left;
            root.left = null;
            node2.right = node;
            flatten(root.right);
        }

    }
    public TreeNode getRight(TreeNode root ){
        while( root.right != null)
            root = root.right;

        return root;
        
    }
}