Leetcode 538:Convert BST to Greater Tree

题目描述：https://leetcode.com/problems/convert-bst-to-greater-tree/#/description

解题思路：后续遍历，每个节点的值等于其自身值加上其已经遍历过的值之和。

AC代码

public class Solution {
int count = 0;
public TreeNode convertBST(TreeNode root) {
if(root == null) return null;
convert(root);
return root;
}

public void convert(TreeNode root){
if(root == null) return;
convert(root.right);
count += root.val;
root.val = count;
convert(root.left);
}
}