AlgoSolveoRoadmap › Stage 1: Foundations (Start Here) › Pattern 5 of 53
DSA pattern guide
Matrix — 2D Arrays
Grids, rows and columns, rotating or walking a matrix in a pattern.
Use it when
Grids, rows and columns, rotating or walking a matrix in a pattern.
Key idea
Think in (row, col) pairs and boundaries. Many tricks are two simple moves combined, like rotate = transpose + reverse each row.
Practise it right here
3 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
- Matrix Diagonal SumEasy
- Transpose MatrixEasy
- Reshape the MatrixEasy
- Rotate ImageMedium
- Spiral MatrixMedium
- Set Matrix ZeroesMedium
- Valid SudokuMedium
- Search a 2D MatrixMedium
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