Representative Matrix problems
Check if a 9x9 Sudoku board is valid by scanning rows, columns, and sub-boxes with hash lookups, ensuring no duplicates exist.
Open problem page#37 Sudoku SolverSolve the Sudoku puzzle by filling empty cells while respecting Sudoku's rules using array scanning and backtracking.
Open problem page#48 Rotate ImageRotate an n x n matrix 90 degrees clockwise in-place using array manipulation and mathematical indexing techniques efficiently.
Open problem page#54 Spiral MatrixGiven an m x n matrix, return all elements in spiral order starting from the top-left corner.
Open problem page#59 Spiral Matrix IIGenerate a spiral matrix of size n x n, filled with elements from 1 to n² in spiral order, for interview-focused solving.
Open problem page#63 Unique Paths IICalculate the number of unique paths from top-left to bottom-right in a grid with obstacles using dynamic programming state transitions.
Open problem page#64 Minimum Path SumCompute the minimum sum from top-left to bottom-right in a grid using state transition dynamic programming efficiently.
Open problem page#73 Set Matrix ZeroesModify the matrix in place by setting rows and columns to zero when an element is zero.
Open problem page#74 Search a 2D MatrixSearch a 2D matrix efficiently using binary search over its linearized index, ensuring correctness in row-major sorted arrays.
Open problem pageMatrix interview questions usually collapse into a small set of repeatable moves. This page groups those GhostInterview problem pages together so you can stay inside one pattern family, compare representative questions, and practice explanations that transfer across multiple prompts. If you are trying to sharpen one interview weakness instead of browsing the entire library, start here.
Why Matrix Matters In Coding Interviews
Interviewers rarely care about the label alone. They care about whether you can recognize when the Matrix pattern applies, explain why it applies, and avoid the failure modes that usually show up under time pressure. That is why this page focuses on the family of problems rather than a single isolated example.
Pattern families that show up here
- Array plus Matrix
- State transition dynamic programming
- Array scanning plus hash lookup
Use this page to narrow the session
Start from this topic hub, choose one or two representative problems, and then open the detailed problem pages only after you know which version of the pattern you want to reinforce.
How To Practice This Topic
The best workflow is to keep the prep block narrow. Pick one easy or medium problem to confirm the base pattern, then one medium or hard problem to test whether the explanation still holds when the constraints tighten. Once the logic is stable, move into GhostInterview to rehearse the live explanation flow.
Focus on transfer, not title count
Solving more Matrix titles is less useful than understanding how the same move changes across examples. Try to describe what stays the same and what changes from one problem to the next.
Use the problem page when you want the exact breakdown
This topic hub is the discovery layer. The single-problem pages are where you get the answer-first summary, examples, constraints, approach, complexity, pitfalls, and solver CTA.
How GhostInterview Fits
GhostInterview works best after you know which pattern family you are inside. Use this page to choose the right Matrix problem, then use the solver to get the answer path, complexity framing, and follow-up support without switching into a generic study flow.
FAQ
What does the Matrix topic usually test in interviews?
Matrix questions usually test whether you can spot the underlying pattern quickly, explain the trade-offs, and move from intuition to implementation without losing clarity.
How should I use this Matrix topic page?
Use it as a pattern hub. Start with the representative problems on this page, compare the common approach, and then open the exact problem page when you want the full breakdown.
How many GhostInterview problem pages are in the Matrix group?
This topic page currently groups 221 indexed GhostInterview problem pages under the Matrix family.
Should I practice this topic before harder patterns?
That depends on your current gaps. If Matrix is already a weak spot in interviews, it is usually better to stabilize it first before moving into more advanced or less frequent patterns.
Where does GhostInterview fit once I pick a Matrix problem?
The topic page narrows the pattern family. The problem page gives the exact breakdown. GhostInterview is the solver layer when you need direct help with execution, complexity, and follow-up handling.
Stay close to the same reasoning family
1,672 overlapping problems
Open topic pageBreadth-First Search197 overlapping problems
Open topic pageDynamic Programming529 overlapping problems
Open topic pageDepth-First Search252 overlapping problems
Open topic pageSimulation171 overlapping problems
Open topic pageHash Table610 overlapping problems
Open topic pageNeed direct help once you choose a Matrix problem?
Use GhostInterview as the solver layer after you select the exact prompt. Capture the question, get the answer path and complexity framing, and keep the workflow inside the same topic family.