Why This Matters
Sorting makes order usable. Once data is sorted, binary search, duplicate removal, interval merging, sweep-line algorithms, and many database-style joins become simpler.
Core Idea
Comparison sorting can only learn order by comparing pairs. General comparison sorting has an lower bound in the worst case.
| Algorithm | Typical role |
|---|---|
| bubble sort | teaching baseline, not production |
| insertion sort | small or nearly sorted arrays |
| merge sort | stable sorting |
| quicksort | fast average-case in-place sorting |
Worked example: sorting meeting intervals by start time turns overlap detection into a single left-to-right scan.
Common Mistakes
- Treating all sorts as identical. Stability, memory, constants, and input distribution matter.
- Using bubble sort outside teaching.
- Forgetting that non-comparison sorts need assumptions about keys.
Exercises
- Identify whether a sort must be stable for sorting records by two keys.
- Explain why sorted data makes binary search possible.
- Compare merge sort and quicksort on memory use.
Next Topics
References
- Cormen, Leiserson, Rivest, Stein. Introduction to Algorithms (4th ed., 2022). Ch. 2, 6, 7, 8.
- Knuth. The Art of Computer Programming, Volume 3: Sorting and Searching (2nd ed., 1998).