Revquix 80

Revquix 80 is a curated list of 80 DSA problems that cover every core topic, from arrays to dynamic programming, in five languages.

It is a focused first pass through DSA: the problems that teach the ideas behind most coding interview questions, in a sensible order, with nothing extra. Every problem is judged against hidden test cases in Python, C++, Java, JavaScript and TypeScript, and each section runs from easy to hard.

What you will practise:

• Arrays, Strings and Hashing: 11 problems such as Pair That Hits the Target, No-Repeat Stretch and Quarter Turn.
• Two Pointers and Sliding Window: 7 problems such as Sorted Pair Finder, Three-Flag Sort and Smallest Covering Window.
• Sorting, Binary Search and Intervals: 8 problems such as Shelf Finder, First and Last Seen and Ship It in Time.
• Linked Lists: 6 problems such as Turn the Chain Around, Chain Loop Check and Recently Used Cache.
• Stacks and Queues: 6 problems such as Bracket Balance, Postfix Evaluator and Biggest Bar Rectangle.
• Trees and Binary Search Trees: 11 problems such as Tree Depth, Shared Ancestor and Richest Path.
• Heaps and Greedy: 6 problems such as Most Talked About, K Nearest to Home and Live Median.
• Recursion and Backtracking: 5 problems such as Every Subset, Reusable Coins to Target and Queens Boards.
• Graphs: 8 problems such as Count the Islands, Course Plan Feasible and Word Ladder Steps.
• Dynamic Programming: 9 problems such as Stair Climber, Fewest Coins and Edit Steps.
• Tries, Bit Manipulation and Design: 3 problems such as The Lone Sock, Lit Bits and Prefix Tree.

Work through one section at a time and finish a section before you move on. If a problem feels too hard, try an easier one from the same section first, then come back to it. Every problem comes with worked examples and clear constraints.