1 files changed, 103 insertions, 0 deletions
diff --git a/algorithms/impl/quicksort.py b/algorithms/impl/quicksort.py
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+++ b/algorithms/impl/quicksort.py
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+# Copyright (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is part of the "Sorting algorithms" project.
+# For details, see https://github.com/egor-tensin/sorting-algorithms.
+# Distributed under the MIT License.
+
+from random import randrange, seed
+import sys
+
+from ..algorithm import SortingAlgorithm
+
+
+seed()
+
+
+def _partition(xs, beg, end, select_pivot):
+    pivot = select_pivot(xs, beg, end)
+    xs[pivot], xs[end] = xs[end], xs[pivot]
+    for i in range(beg, end):
+        if xs[i] <= xs[end]:
+            xs[i], xs[beg] = xs[beg], xs[i]
+            beg += 1
+    xs[beg], xs[end] = xs[end], xs[beg]
+    return beg
+
+
+def _quicksort(xs, beg, end, select_pivot):
+    if beg < end:
+        pivot = _partition(xs, beg, end, select_pivot)
+        _quicksort(xs, beg, pivot - 1, select_pivot)
+        _quicksort(xs, pivot + 1, end, select_pivot)
+
+
+def _select_first(xs, beg, end):
+    return beg
+
+
+def _select_second(xs, beg, end):
+    return beg + 1
+
+
+def _select_middle(xs, beg, end):
+    return (beg + end) // 2
+
+
+def _select_last(xs, beg, end):
+    return end
+
+
+def _select_random(xs, beg, end):
+    return randrange(beg, end + 1)
+
+
+def quicksort_first(xs):
+    _quicksort(xs, 0, len(xs) - 1, _select_first)
+    return xs
+
+
+def quicksort_second(xs):
+    _quicksort(xs, 0, len(xs) - 1, _select_second)
+    return xs
+
+
+def quicksort_middle(xs):
+    _quicksort(xs, 0, len(xs) - 1, _select_middle)
+    return xs
+
+
+def quicksort_last(xs):
+    _quicksort(xs, 0, len(xs) - 1, _select_last)
+    return xs
+
+
+def quicksort_random(xs):
+    _quicksort(xs, 0, len(xs) - 1, _select_random)
+    return xs
+
+
+_ALGORITHMS = [
+    SortingAlgorithm('quicksort_first', 'Quicksort (first element as pivot)', quicksort_first),
+    SortingAlgorithm('quicksort_second', 'Quicksort (second element as pivot)', quicksort_second),
+    SortingAlgorithm('quicksort_middle', 'Quicksort (middle element as pivot)', quicksort_middle),
+    SortingAlgorithm('quicksort_last', 'Quicksort (last element as pivot)', quicksort_last),
+    SortingAlgorithm('quicksort_random', 'Quicksort (random element as pivot)', quicksort_random),
+]
+
+
+def _parse_args(args=None):
+    if args is None:
+        args = sys.argv[1:]
+    return list(map(int, args))
+
+
+def main(args=None):
+    xs = _parse_args(args)
+    print(quicksort_first(list(xs)))
+    print(quicksort_second(list(xs)))
+    print(quicksort_middle(list(xs)))
+    print(quicksort_last(list(xs)))
+    print(quicksort_random(list(xs)))
+
+
+if __name__ == '__main__':
+    main()