538. Convert BST to Greater Tree

最新推荐文章于 2024-06-02 16:09:57 发布

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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。转换后的树中每个节点的值等于原BST中该节点的值加上所有大于该值的节点之和。文章详细解释了采用右根左遍历顺序进行转换的过程。

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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.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    int sum=0;
    public TreeNode convertBST(TreeNode root) {
        if(root==null)return null;
        
        convertBST(root.right);
        
        root.val+=sum;
        sum=root.val;
        
        convertBST(root.left);
        
        return root;
    }
}

根据右根左的顺序