Project Euler 872 - Recursive Tree

Official link: https://projecteuler.net/problem=872

Thought Process

After drawing a few trees a few patterns emerge. 

1. The height of the tree is log2(n) + 1

2. The children of node n are always [n-1, n-2, n-4, n-8, n-16, n-2^k]

3. The children of n-1 are always [n-3, n-5, n-9, etc]

Essentially there are patterns relating to 2^n.

Once you ask yourself the question: What is the parent of node x, then answer becomes clear.

Interactive Code

Input 2 integers separated by a space (n, x)

Code will output f(n, x)