538. Convert BST to Greater Tree

最新推荐文章于 2025-05-12 08:35:32 发布

原创最新推荐文章于 2025-05-12 08:35:32 发布 · 205 阅读

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本文介绍了一种将二叉搜索树（BST）转换为Greater Tree的方法，其中每个节点的值变为原值加上所有大于该值的节点之和。通过递归地调整右子树、更新节点值并最后调整左子树的过程，实现这一转换。

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

/**
 * 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:
    void convert(TreeNode* root, int& sum){
        if(root == NULL)    return;
        convert(root->right, sum);
        root->val += sum;
        sum = root->val;
        convert(root->left, sum);
    }

    TreeNode* convertBST(TreeNode* root) {
        int sum = 0;
        convert(root, sum);
        return root;
    }
};