Browse Curriculum
The Matrices Pattern
A 2D grid is a graph whose neighbours are implicit: each cell connects to the cells beside it. Most matrix problems are BFS, DFS or DP with row and column bookkeeping, plus in-place tricks for rotation and traversal.
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Interactive problems1
Free to openHow to recognise a matrices problem
The input is a 2D grid and the question involves islands, regions, flood fill, spiral or diagonal traversal, path counting, or rotating and transposing in place.
Time and space complexity
O(rows × cols) for a full traversal. In-place transformations keep space at O(1) beyond the input.
Matrices practice problems
Each problem pairs a worked explanation with an interactive visualizer you step through yourself, plus the implementation in JavaScript, Python, Java and C++.
Related patterns and concepts
Matrices is one of the 16 coding interview patterns, and its problems also appear in the DSA 75 interview sprint.