exercism/elixir/pop-count

Eliud's Eggs

Welcome to Eliud's Eggs on Exercism's Elixir Track. If you need help running the tests or submitting your code, check out HELP.md.

Introduction

Your friend Eliud inherited a farm from her grandma Tigist. Her granny was an inventor and had a tendency to build things in an overly complicated manner. The chicken coop has a digital display showing an encoded number representing the positions of all eggs that could be picked up.

Eliud is asking you to write a program that shows the actual number of eggs in the coop.

The position information encoding is calculated as follows:

1. Scan the potential egg-laying spots and mark down a 1 for an existing egg or a 0 for an empty spot.
2. Convert the number from binary to decimal.
3. Show the result on the display.

Example 1:

Chicken Coop:
 _ _ _ _ _ _ _
|E| |E|E| | |E|

Resulting Binary:
 1 0 1 1 0 0 1

Decimal number on the display:
89

Actual eggs in the coop:
4

Example 2:

Chicken Coop:
 _ _ _ _ _ _ _ _
| | | |E| | | | |

Resulting Binary:
 0 0 0 1 0 0 0 0

Decimal number on the display:
16

Actual eggs in the coop:
1

Instructions

Your task is to count the number of 1 bits in the binary representation of a number.

Restrictions

Keep your hands off that bit-count functionality provided by your standard library! Solve this one yourself using other basic tools instead.

Source

Created by

• @kahgoh

Based on

Christian Willner, Eric Willigers - https://forum.exercism.org/t/new-exercise-suggestion-pop-count/7632/5