# Hardest Beginner Challenges

The 5 hardest “easy” challenges are listed below:

• Vowel Square: Requires finding a 2x2 square of vowels in a larger matrix.
• Scale Balancing: Requires looping through an array of weights to determine if a scale can be perfectly balanced.
• Correct Path: Requires traversing through a partially finished path in an NxN matrix and finishing the path.
• Closest Enemy II: Requires checking the distance between certain points in a NxM matrix.

# Challenge Description

Take an input string parameter and determine if exactly 3 question marks exist between every pair of numbers that add up to 10. If so, return true, otherwise return false. Some examples test cases are below:

# Analysis

This challenge requires several layers of logic to get right, which is why it can be difficult to come up with a solution at first. It requires looping through the string and maintaining the position of every pair of numbers that add up to 10. If you do find two numbers that add up to 10, then you will need to determine if exactly 3 specific characters exist somewhere between these two indices.

• 35% of users who submitted a solution in Ruby didn’t get a perfect score.
• The average number of lines for a solution is 15–29.

# Sample Solutions

Below is a very concise and elegant solution written in Python by the #3 ranked user on Coderbyte, Qlogin.