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Nearly Sorted Initial Order

Animation, code, analysis, and discussion of 8 sorting algorithms on nearly sorted initial order.

← Back to all algorithms and initial conditions

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How to use: Press "Play all", or choose the button.

Play All	Play animation Insertion	Play animation Selection	Play animation Bubble	Play animation Shell
Play All	Play animation Merge	Play animation Heap	Play animation Quick	Play animation Quick3

DISCUSSION

Sorting nearly sorted data is quite common in practice. Some observations:

Insertion sort is the clear winner on this initial condition.
Bubble sort is fast, but insertion sort has lower overhead.
Shell sort is fast because it is based on insertion sort.
Merge sort, heap sort, and quick sort do not adapt to nearly sorted data.

Insertion sort provides a O(n²) worst case algorithm that adapts to O(n) time when the data is nearly sorted. One would like an O(n·lg(n)) algorithm that adapts to this situation; smoothsort is such an algorithm, but is complex. Shell sort is the only sub-quadratic algorithm shown here that is also adaptive in this case.

KEY

Black values are sorted.
Gray values are unsorted.
A red triangle marks the algorithm position.
Dark gray values denote the current interval (shell, merge, quick).
A pair of red triangles marks the left and right pointers (quick).

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