Recursion
12 problems · 10 with full explanations
4 Easy2 Medium4 Hard
Recursion solves a problem by calling itself with a smaller sub-problem. Every recursive solution needs: a base case (to stop) and a recursive case (to reduce). Stack space is O(depth). Convert deep recursion to iteration with an explicit stack when stack overflow is a concern.
How to practice
To practice Recursion problems effectively, start with the Easy problems listed below, trace through each solution on paper, then re-implement without looking. When you can recognise the recursion pattern within 30 seconds of reading a new problem, move on to Medium difficulty. Use the related topic pages and our study guide for a structured progression.
Start here (Easy + explained)
All Recursion problems
- 25.Reverse Nodes in k-GroupHard
- 241.Different Ways to Add ParenthesesMedium
- 273.Integer to English WordsHard
- 326.Power of ThreeEasy
- 342.Power of FourEasy
- 344.Reverse StringEasy
- 726.Number of AtomsHard
- 761.Special Binary StringUnknown
- 1106.Parsing A Boolean ExpressionHard
- 1545.Find Kth Bit in Nth Binary StringEasy
- 1823.Find the Winner of the Circular GameMedium
- 3307.Find the K-th Character in String Game IIUnknown