Knowledge Guide
HomeDSARecursion

7 Number Frequency

Problem Statement

Write a Recursive Solution to Count occurrences of an Element in an Array.

Given an array of integers and a key element, write a recursive solution to count the occurrences of the key element in the array.

Examples:

Sr#ArrayInput KeyOutputDescription
1[2, 4, 6, 8, 4]42The key element 4 occurs twice in the array.
2[1, 3, 5, 7, 9]20The key element 2 does not exist in the array.
3[1, 2, 2, 2, 3]23The key element 2 occurs three times in the array.

Try it yourself

Try solving this question here:

🤖 Don't fully get this? Learn it with Claude

Stuck on 7 Number Frequency? Open Claude, copy a block below, and it'll teach you this exact concept — visually and interactively.

🎨 Explain it visually

Build the mental picture, not memorization.

I just read a lesson on **7 Number Frequency** (DSA) and want to truly understand it. Explain 7 Number Frequency from first principles using ONE vivid real-world analogy and a visual mental model — draw it as ASCII art or a clear step-by-step diagram — with a concrete example using real numbers. Then ask me one question to check I got the mental picture, and wait for my reply. If you're unsure or a claim isn't standard, say so and reason from first principles instead of guessing.
🤔 Walk me through it (interactive)

Socratic — adapts to where you're stuck.

Teach me **7 Number Frequency** interactively. Ask me ONE guiding question at a time, wait for my answer, and adapt to my confusion — build the idea with me step by step instead of explaining it all at once. If you're unsure or a claim isn't standard, say so and reason from first principles instead of guessing.
🧪 Quiz me & fix my gaps

Active recall exposes what you missed.

Quiz me on **7 Number Frequency** with 5 questions, easy to tricky, ONE at a time. Tell me if each answer is right; at the end, explain clearly what I got wrong and why. If you're unsure or a claim isn't standard, say so and reason from first principles instead of guessing.
🧠 Make it stick

Intuition + hook + flashcards for long-term memory.

Help me remember **7 Number Frequency** for the long term: give the one-sentence intuition, a memorable hook/mnemonic, a tiny worked example, and 3 active-recall flashcards (Q -> A). If you're unsure or a claim isn't standard, say so and reason from first principles instead of guessing.

📝 My notes