Posted in Python onDecember 18, 2013
# -*- coding: utf-8 -*- def insertion_sort(A): """插入排序,作为桶排序的子排序""" n = len(A) if n <= 1: return A B = [] # 结果列表 for a in A: i = len(B) while i > 0 and B[i-1] > a: i = i - 1 B.insert(i, a); return B def bucket_sort(A): """桶排序,伪码如下: BUCKET-SORT(A) 1 n ← length[A] // 桶数 2 for i ← 1 to n 3 do insert A[i] into list B[floor(nA[i])] // 将n个数分布到各个桶中 4 for i ← 0 to n-1 5 do sort list B[i] with insertion sort // 对各个桶中的数进行排序 6 concatenate the lists B[0],B[1],...,B[n-1] together in order // 依次串联各桶中的元素 桶排序假设输入由一个随机过程产生,该过程将元素均匀地分布在区间[0,1)上。 """ n = len(A) buckets = [[] for _ in xrange(n)] # n个空桶 for a in A: buckets[int(n * a)].append(a) B = [] for b in buckets: B.extend(insertion_sort(b)) return B if __name__ == '__main__': from random import random from timeit import Timer items = [random() for _ in xrange(10000)] def test_sorted(): print(items) sorted_items = sorted(items) print(sorted_items) def test_bucket_sort(): print(items) sorted_items = bucket_sort(items) print(sorted_items) test_methods = [test_sorted, test_bucket_sort] for test in test_methods: name = test.__name__ # test.func_name t = Timer(name + '()', 'from __main__ import ' + name) print(name + ' takes time : %f' % t.timeit(1))
python算法学习之桶排序算法实例(分块排序)
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