1038. Binary Search Tree to Greater Sum Tree

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:

• The left subtree of a node contains only nodes with keys less than the node's key.
• The right subtree of a node contains only nodes with keys greater than the node's key.
• 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:

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

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

wdnmd你知道和538一样害po出来？？