Binary Search Tree to Greater Sum Tree

Similar Problems:

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]

Note:

- 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.

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

- Solution:

// Blog link: https://code.dennyzhang.com/binary-search-tree-to-greater-sum-tree // Basic Idea: tree transeveral: right, middle, left /** * Definition for a binary tree node. * type TreeNode struct { * Val int * Left *TreeNode * Right *TreeNode * } */ func dfs(root *TreeNode, val *int) { if root == nil { return } if root.Right != nil { dfs(root.Right, val) } *val += root.Val root.Val = *val if root.Left != nil { dfs(root.Left, val) } } func bstToGst(root *TreeNode) *TreeNode { val := 0 dfs(root, &val) return root }