Matrix and Grid coding problems

Matrix problems test 2D indexing: spiral order, rotations, grid walks, flood fills and 2D prefix sums.

18 problems: 10 easy, 8 medium, 0 hard. Free to read; a free account solves them and earns XP and Aura.

1. Count Black CellsPractice · +10 XP · matrix, traversal, beginnereasy
2. Matrix Anti-Diagonal SumPractice · +10 XP · matrix, traversaleasy
3. Matrix Column SumPractice · +10 XP · matrixeasy
4. Matrix Diagonal ElementsPractice · +10 XP · matrix, traversaleasy
5. Matrix Element SumPractice · +10 XP · matrix, traversal, loopseasy
6. Matrix Row SumsPractice · +10 XP · matrix, loops, basiceasy
7. Matrix Saddle PointsPractice · +10 XP · matrix, grid, traversaleasy
8. Matrix Spiral PrintPractice · +10 XP · matrix, traversaleasy
9. Matrix TransposePractice · +10 XP · matrixeasy
10. Sum of Matrix DiagonalsPractice · +10 XP · matrix, traversaleasy
11. Distinct Row CountsPractice · +20 XP · matrix, hashing, data structuresmedium
12. Distinct Subgrid ValuesPractice · +20 XP · matrix, prefix sums, hash setmedium
13. Matrix Neighbors SumPractice · +20 XP · matrix, bfs, hash mapmedium
14. Matrix Zero Sum SubgridsPractice · +20 XP · matrix, prefix sums, hash mapmedium
15. Maximum Rectangle SumPractice · +20 XP · matrix, prefix sums, kadane's algorithmmedium
16. Maximum Sum SubmatrixPractice · +20 XP · matrix, prefix sumsmedium
17. Minimum Path Sum in GridPractice · +20 XP · matrix, dynamic programming, bfsmedium
18. Most Frequent Row XORPractice · +20 XP · matrix, hash map, frequencymedium