快排、堆排和归并排序的Python实现

来源：互联网发布：手机办公软件编辑：程序博客网时间：2024/04/28 06:20

快速排序：

#! /usr/bin/env python#coding=utf-8import random,copydef partition(lst,left,right):    pivot = lst[left]    pivot_index = left    left = left + 1    while True:        # when pivot as lst[left] start from left        while left <= right and lst[left] <= pivot:            left = left + 1        while left <= right and lst[right] >= pivot:            right = right - 1        if left <= right:            lst[left],lst[right] = lst[right],lst[left]        else:            break    lst[pivot_index],lst[right] = lst[right],lst[pivot_index]    return rightdef quick_sort_helper(lst,start,end):    if (start < end):        split_position = partition(lst,start,end)        quick_sort_helper(lst,start,split_position-1)        quick_sort_helper(lst,split_position+1,end)def quick_sort(lst):    quick_sort_helper(lst,0,len(lst)-1)    def quick_sort_helper2(lst,left,right):    if left < right:        pivot_index = right        pivot = lst[pivot_index]        i = left        k = left        while i < right:            if lst[i] <= pivot:                lst[k],lst[i] = lst[i],lst[k]                k = k + 1            i = i + 1        lst[k],lst[pivot_index] = lst[pivot_index],lst[k]        quick_sort_helper2(lst,left,k-1)        quick_sort_helper2(lst,k+1,right)        def quick_sort2(lst):    quick_sort_helper2(lst,0,len(lst)-1)        if  __name__ == '__main__':    lst = [random.randint(0,20) for i in range(10)]    lst2 = copy.deepcopy(lst)    lst2.sort()    print(lst)    print(lst2)    quick_sort2(lst)    print(lst)

堆排序：

#! /usr/bin/env python#coding=utf-8import random,copydef heap_sort_helper(lst,left,right):    # max heapify    current_value = lst[left]    child = 2 * left + 1    while (child <= right):        if (child < right and lst[child] < lst[child+1]):            child  = child + 1        if (current_value > lst[child]):            break        else:            lst[(child-1)>>1] = lst[child]            child = 2 * child + 1    lst[(child-1)>>1] = current_value    def heap_sort(lst):    # build heap    for i in range((len(lst)-1)>>1,-1,-1):        heap_sort_helper(lst,i,len(lst)-1)    for i in range(len(lst)-1,0,-1):        lst[i],lst[0] = lst[0],lst[i]        heap_sort_helper(lst,0,i-1)if  __name__ == "__main__":    lst = [random.randint(0,20) for i in range(10)]    lst2 = copy.deepcopy(lst)    lst2.sort()    print(lst)    print(lst2)    heap_sort(lst)    print(lst)

归并排序：

#! /usr/bin/env python#coding=utf-8import randomdef mergesort(seq):    mid = len(seq) // 2    lft,rht = seq[:mid],seq[mid:]    if len(lft) > 1:         lft = mergesort(lft)    if len(rht) > 1:        rht = mergesort(rht)    res = []    while lft and rht:        #using pop to reduce data movements        if lft[-1] >= rht[-1]:            res.append(lft.pop())        else:            res.append(rht.pop())    res.reverse()    return (lft or rht) + resdef main():    seq = [random.randint(0,20) for i in range(10)]    print(seq)    seq = mergesort(seq)    print(seq)    if __name__ == "__main__":    main()

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