Day 2: Find First Duplicate

Learning Goals

• Practice algorithmic problem solving

Instructions

Given an Array, find the first duplicate value that occurs. If there are no duplicates, return -1.

Input: [2, 1, 3, 3, 2]
Output: 3

Input: [1, 2, 3, 4]
Output: -1

Use the language of your choosing. We've included starter files for some languages where you can pseudocode, explain your solution and code.

Before you start coding

1. Rewrite the problem in your own words
2. Validate that you understand the problem
3. Write your own test cases
4. Pseudocode
5. Code!

And remember, don't run our tests until you've passed your own!

How to run your own tests

Ruby

1. cd into the ruby folder
2. ruby <filename>.rb

JavaScript

1. cd into the javascript folder
2. node <filename>.js

How to run our tests

Ruby

1. cd into the ruby folder
2. bundle install
3. rspec

JavaScript

1. cd into the javascript folder
2. npm i
3. npm test