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Linear & Sentinel Search
Scan until found. Unbeatable on unsorted or tiny data, and the baseline every other search is measured against.
What to know
- No ordering or preprocessing required; works on any iterable.
- A sentinel copy of the target at the end removes the bounds check per step.
- Branch prediction makes linear scans of small arrays faster than "smarter" searches.
In the wild: grep over a file, finding an element in a small config list, DOM querySelector fallbacks.
Algorithms to reach for
Linear scan
O(n)Find in unsorted data, short-circuit on hit
Sentinel search
O(n)Micro-optimized scan for hot loops
Practice problems — with full guides
Each problem has its own page: progressive hints, how to approach it, and the full solution.