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Decode the Coding Interview in Rust: Real-World Examples

Flip Equivalent Binary Trees

Explore how to verify if two binary trees are flip equivalent by recursively swapping child subtrees in Rust. Understand base conditions, recursive checks, and complexity measures to solve this problem effectively.

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Description

Let’s start by defining what a flip operation for a binary tree is. We can define it as:

“Choosing any node and swapping the right and left child subtrees.”

A binary tree, T, is flip equivalent to another binary tree, S, if we can make T equal to S after some number of flip operations.

Given the roots of two binary trees, root1 and root2, you have to find out whether the trees are flip equivalent to each other or not. The flip_equiv function should return true if the binary trees are equivalent. Otherwise, it will return false.

Example

Let’s look at the example below:

Do it yourself!

Rust 1.57.0
fn flip_equiv(root: Option<Rc<RefCell<TreeNode>>>, root1: Option<Rc<RefCell<TreeNode>>>)->bool {
        return false;
  }

Solution

We implement the flip_equiv function using recursion. Like any recursive function, we start by defining the base conditions. We have two base conditions:

  1. If root1 or root2 is null, they are equivalent if and only if they are both None.

  2. If root1 and root2 have different values, they aren’t equivalent.

Lastly, we move on to the ...