Write a method that removes duplicate String values from a List while preserving the original order of first occurrences. The method should return a new List with unique values only.

Examples:

Input: ['apple', 'banana', 'apple', 'orange', 'banana'] Output: ['apple', 'banana', 'orange'] Explanation: Duplicates removed, first occurrence kept Input: ['hello', 'world', 'hello'] Output: ['hello', 'world'] Explanation: Second 'hello' is removed Input: ['a', 'b', 'c'] Output: ['a', 'b', 'c'] Explanation: No duplicates, list unchanged Input: [] Output: [] Explanation: Empty list remains empty
Apex Code Editor
Sign in to Submit

Welcome to Lightning Challenge!

Create an Account

Sign up to track your progress, earn points, and compete with others. Your solutions will be saved automatically.

Create account

How It Works

  • • Write your solution in the code editor
  • • Connect your Salesforce org to test
  • • Submit to check if your solution passes
  • • Use hints if you get stuck

Note

You can test your code by connecting to Salesforce, but to save your progress and earn points, you'll need to create an account. Your solutions and achievements will be tracked automatically once you're logged in.