Decode the Coding Interview in C++: Real-World Examples/

...

/

Flip Equivalent Binary Trees

Flip Equivalent Binary Trees

Understand and solve the interview question "Flip Equivalent Binary Trees".

We'll cover the following...

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 flipEquiv function should return true if the binary trees are equivalent. Otherwise, it will return false.

Example

Let’s look at the example below:

Coding exercise

main.cpp
TreeNode.h
#include "TreeNode.h"
bool flipEquiv(TreeNode* root1, TreeNode* root2) {
    // write your code here
    return false;
}
Flip equivalent binary tree

Solution

We implement the flipEquiv 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 null.

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

Lastly, we move on to the recursive part and check whether the children of root1 are equivalent to the children of root2. We pair the children in two different ways:

  1. Compare the left subtree of root1 with the
...