Convert BST to Greater Tree

•  描述
•  笔记
•  数据
•  评测

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.

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Yes

样例

Given a binary search Tree ｀{5,2,3}｀:

              5            /   \           2     13

Return the root of new tree

             18            /   \          20      13

解题思路：以右子树为先的中序遍历，每次记录到当前节点的和，然后赋值给当前节点即可。

class Solution {public:    /**     * @param root the root of binary tree     * @return the new root     */        int ans=0;        int dfs(TreeNode* root){                      if(root==NULL)return 0;           dfs(root->right);           ans=root->val+ans;           root->val=ans;           dfs(root->left);}    TreeNode* convertBST(TreeNode* root) {        // Write your code here       dfs(root);       return root;    }};