lintcode(661)Convert BST to Greater Tree

最新推荐文章于 2019-06-20 16:15:31 发布

原创最新推荐文章于 2019-06-20 16:15:31 发布 · 820 阅读

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#java #lintcode #简单算法

本文介绍了一种将二叉搜索树转换为Greater Tree的方法，通过递归算法调整每个节点的值，使其等于原值加上所有大于该值的节点之和。

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描述：

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.

样例：

Given a binary search Tree ｀{5,2,3}｀:

              5
            /   \
           2     13

Return the root of new tree

思路：

采用递归，每个节点的值等于右节点的值加自身的值，左节点的值等于右节点加根节点的值。

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root the root of binary tree
     * @return the new root
     */
    public TreeNode convertBST(TreeNode root) {
        // Write your code here
        if(root == null){
            return root;
        }
        int temp = search(root , 0);
        return root;
    }
    
    public int search(TreeNode root , int count){
        if(root == null){
            return 0;
        }
        int right = search(root.right , count);
        int left = search(root.left , count + root.val + right);
        int result = right + left + root.val;
        root.val += right + count;
        return result;
    }
}