lintcode(661)Convert BST to Greater Tree

描述：

Given a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus sum of all keys greater than the original key in BST.

样例：

Given a binary search Tree ｀{5,2,3}｀:

              5            /   \           2     13

Return the root of new tree 

思路：

采用递归，每个节点的值等于右节点的值加自身的值，左节点的值等于右节点加根节点的值。

/** * Definition of TreeNode: * public class TreeNode { *     public int val; *     public TreeNode left, right; *     public TreeNode(int val) { *         this.val = val; *         this.left = this.right = null; *     } * } */public class Solution {    /**     * @param root the root of binary tree     * @return the new root     */    public TreeNode convertBST(TreeNode root) {        // Write your code here        if(root == null){            return root;        }        int temp = search(root , 0);        return root;    }        public int search(TreeNode root , int count){        if(root == null){            return 0;        }        int right = search(root.right , count);        int left = search(root.left , count + root.val + right);        int result = right + left + root.val;        root.val += right + count;        return result;    }}