Merge Two Sorted Lists

Take two already-sorted lists of integers and merge them into one sorted list. Handle null inputs by treating them as empty lists. Both input lists are sorted in ascending order, and the output should also be sorted in ascending order.

Examples:

Input: list1 = [1, 3, 5], list2 = [2, 4, 6] Output: [1, 2, 3, 4, 5, 6] Explanation: Merge two sorted lists into one sorted list Input: list1 = [1, 2, 3], list2 = [] Output: [1, 2, 3] Explanation: When one list is empty, return the other list Input: list1 = null, list2 = [1, 2] Output: [1, 2] Explanation: Null inputs are treated as empty lists Input: list1 = null, list2 = null Output: [] Explanation: Both null inputs result in an empty list Input: list1 = [1, 1, 2], list2 = [1, 3, 3] Output: [1, 1, 1, 2, 3, 3] Explanation: Duplicates are preserved in the merged list
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

Contest Alert

🏆 #CodeEveryDay Jan 2026

Contest runs January 1 - 31. Complete challenges to climb the leaderboard!

Points are calculated for challenges completed during the contest period.