Title
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.
Example:
Input: The root of a Binary Search Tree like this: 5 /
2 13
Output: The root of a Greater Tree like this: 18 /
20 13
对二叉排序树，把每个节点的值设置为比它大的节点的总和，因此需要先right,再left
Solution
//cpp:
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int sum=0;
TreeNode* convertBST(TreeNode* root) {
if(root){
convertBST(root->right);
sum+=root->val;
root->val=sum;
convertBST(root->left);
}
return root;
}
};