Lesson 23 / 42

Linear Search

Check every element until you find the target. O(n), works on any data.

The baseline

Walk left to right, comparing each item. Best case O(1) (first slot), worst and average O(n). No sorting or extra memory required — the fallback when nothing else applies.

Implementation

Return the index, or -1 if absent.

def linear_search(arr, target):
    for i, x in enumerate(arr):
        if x == target:
            return i
    return -1

When it's the right call

Small or unsorted data, linked lists (no random access), or when you'd spend more sorting than searching once.