1038. Binary Search Tree to Greater Sum Tree**

1038. Binary Search Tree to Greater Sum Tree**

https://leetcode.com/problems/binary-search-tree-to-greater-sum-tree/

题目描述

Given the root of a binary search tree with distinct values, modify it so that every node has a new value equal to the sum of the values of the original tree that are greater than or equal to node.val.

As a reminder, a binary search tree is a tree that satisfies these constraints:

1. The left subtree of a node contains only nodes with keys less than the node’s key.
2. The right subtree of a node contains only nodes with keys greater than the node’s key.
3. Both the left and right subtrees must also be binary search trees.

Example 1:

Input: [4,1,6,0,2,5,7,null,null,null,3,null,null,null,8]
Output: [30,36,21,36,35,26,15,null,null,null,33,null,null,null,8]

Constraints:

• The number of nodes in the tree is between 1 and 100.
• Each node will have value between 0 and 100.
• The given tree is a binary search tree.

Note: This question is the same as 538: https://leetcode.com/problems/convert-bst-to-greater-tree/

C++ 实现 1

和 538. Convert BST to Greater Tree* 题目一样.

class Solution {
private:
    int sum = 0;
    void inorder(TreeNode *root) {
        if (!root) return;
        inorder(root->right);
        root->val += sum;
        sum = root->val;
        inorder(root->left);
    }
public:
    TreeNode* bstToGst(TreeNode* root) {
        inorder(root);
        return root;
    }
};