Depth-First Search on Trees | Dataford Interview Questions

How would you solve a tree problem using depth-first search?

Given the root of a binary tree, return the sum of all node values in the tree. You may solve it recursively or iteratively, but the traversal must use depth-first search.

Function

def tree_sum(root):

Input

root: the root node of a binary tree, or None

Output

Return an integer, the sum of every node value in the tree.

Constraints

0 <= number of nodes <= 10^5
-10^4 <= node.val <= 10^4
The input is a valid binary tree

Function Signature

def tree_sum(root):

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Problem