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Decode the Coding Interview in Rust: Real-World Examples

Binary Tree Maximum Path Sum

Explore how to find the maximum path sum in a binary tree with a Rust implementation. Understand the recursion and decisions needed to track the highest sum path, including paths excluding the root. This lesson shows you the method to solve and optimize this common interview problem using depth-first traversal and path contribution calculations.

We'll cover the following...

Description

A path in a binary tree is defined as:

A sequence of nodes such that each pair of adjacent nodes must have an edge connecting them. A node can only be included in a path at most once. Moreover, including the root in the path is not compulsory.

The path sum can be calculated by adding up all nodes’ values in the path. To solve this problem, we will calculate the maximum path sum given the root of a binary tree so that there won’t be any greater path than it in the tree.

Example

Let’s discuss the example below:

Do it yourself!

Rust 1.57.0
fn max_path_sum(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
        return -1;
}

Solution

We’ll start by simplifying the problem and looking at the implementation of the max_contrib(node) function which takes a node as an argument and computes a maximum contribution that this node and one or none ...