Practice problems across 75+ categories
Practice problems frequently asked at Meta • 2900 problems | 652 Easy | 1528 Medium | 703 Hard
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 511 | Count Unguarded Cells in the Grid | Medium | ArrayMatrixSimulation |
| 512 | Count Unhappy Friends | Medium | ArraySimulation |
| 513 | Count Unique Characters of All Substrings of a Given String | Hard | Hash TableStringDynamic Programming |
| 514 | Count Univalue Subtrees | Medium | TreeDepth-First SearchBinary Tree |
| 515 | Count Unreachable Pairs of Nodes in an Undirected Graph | Medium | Depth-First SearchBreadth-First SearchUnion Find |
| 516 | Count Valid Paths in a Tree | Hard | MathDynamic ProgrammingTree |
| 517 | Count Visited Nodes in a Directed Graph | Hard | Dynamic ProgrammingGraphMemoization |
| 518 | Count Vowel Strings in Ranges | Medium | ArrayStringPrefix Sum |
| 519 | Count Vowel Substrings of a String | Easy | Hash TableString |
| 520 | Count Ways To Build Good Strings | Medium | Dynamic Programming |
| 521 | Count Ways to Build Rooms in an Ant Colony | Hard | MathDynamic ProgrammingTree |
| 522 | Count Ways to Distribute Candies | Hard | Dynamic Programming |
| 523 | Count Ways to Group Overlapping Ranges | Medium | ArraySorting |
| 524 | Count Ways to Make Array With Product | Hard | ArrayMathDynamic Programming |
| 525 | Count Words Obtained After Adding a Letter | Medium | ArrayHash TableString |
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