AlgoSolveoRoadmap › Stage 1: Foundations (Start Here) › Pattern 2 of 53
DSA pattern guide
Arrays — Basics
Reading, updating and rearranging an array in place; tracking a best-so-far value in one pass.
Use it when
Reading, updating and rearranging an array in place; tracking a best-so-far value in one pass.
Key idea
Walk the array once with an index, keep a 'write' pointer for in-place edits, and keep running variables (min, max, count) instead of re-scanning.
Practise it right here
4 original problems for this pattern in our free in-browser console. Write Java, Python or JavaScript and get an instant verdict, no install needed.
Open the practice consolePractice problems, in order
- Find Numbers with Even Number of DigitsEasy
- Remove ElementEasy
- Remove Duplicates from Sorted ArrayEasy
- Merge Sorted ArrayEasy
- Check if Array Is Sorted and RotatedEasy
- Squares of a Sorted ArrayEasy
- Best Time to Buy and Sell StockEasy
- Rotate ArrayMedium
How to practise this pattern
- Read the problem and look for the signal above before writing any code.
- Say the brute force out loud, with its time complexity, then ask what work it repeats.
- Apply the key idea and write the optimised version yourself.
- If you're stuck for more than 10 minutes, take one small hint, not the full solution.
- Move to the next problem only when you can explain why this pattern fits.
Stuck on one of these?
The AlgoSolveo extension (free, launching soon) sits beside the LeetCode problem and gives the smallest hint that gets you moving, never the full answer. Solved problems tick off on your roadmap.
Join the extension waitlistTrack it on the roadmap