Searching Algorithms

This lesson covers linear search and binary search — the two fundamental searching algorithms in the OCR A-Level Computer Science (H446) specification. Understanding when and why to use each is essential.

---

What is Searching?

Searching is the process of finding a specific item (the target or key) within a collection of data. The two main approaches are:

Algorithm	Description	Requirement
Linear search	Check each item one by one	Works on any data (sorted or unsorted)
Binary search	Repeatedly halve the search space	Requires sorted data

---

Linear Search

Linear search (also called sequential search) checks each element in the collection one at a time, from the first to the last, until the target is found or the end is reached.

Pseudocode (OCR Style)

function linearSearch(data, target, size)
    for i = 0 to size - 1
        if data[i] == target then
            return i
        endif
    next i
    return -1
endfunction

Python Implementation

def linear_search(data, target):
    for i in range(len(data)):
        if data[i] == target:
            return i
    return -1