🔍 How to Find Things in Lists — Search Algorithms

Watch linear and binary search work step by step. Understand when each algorithm shines — and when it doesn't.

Designed with the WJEC specification in mind
CS GCSE §1.4CS A-Level Unit 1CS A-Level Unit 3

🤔 What are search algorithms?

Search algorithms help computers find specific items in lists. Linear search checks every item one by one. Binary search is smarter — it keeps cutting the list in half, but only works on sorted lists!

🍕 Analogy: Linear search is like looking for a book by checking every shelf. Binary search is like opening a dictionary to the middle and deciding "too early" or "too late" to find your word faster!
⚙️

Controls

Unchecked
Checking
In range
Midpoint
Eliminated
Found!
Generate an array and pick a target number to search for.
Comparisons0
Array Size15
StatusReady
📊

Linear Search

Checks each element one by one from the start until the target is found or the end is reached.

Requirement: None — works on any array (sorted or unsorted).

When to use: Small arrays, unsorted data, or when the target is likely near the start.

Best
O(1)
Average
O(n)
Worst
O(n)
⚡

Binary Search

Repeatedly halves the search space by comparing the target with the middle element.

Requirement: Array must be sorted first.

When to use: Large sorted arrays. Massively faster than linear for big data sets.

Best
O(1)
Average
O(log n)
Worst
O(log n)
📝

Exam Tips

  • GCSE: Know that binary search only works on sorted data
  • A-Level: Remember the time complexities: Linear O(n), Binary O(log n)
  • Key point: Binary search halves the search space each step
  • Common mistake: Trying to use binary search on unsorted arrays