Python 算法基础 排序实现

写在前面

重新学习Python，打算从最基本的排序算法开始实现。
这些算法的理论和知识在网上一搜都是大把大把的，因此这里不写理论知识，直接放代码。
冒泡排序、直接插入排序、希尔排序、计数排序、堆排序、归并排序、快速排序均基于Python3实现。

随机生成待排序数组

import randomdef generateRandomData(num):    # num表示带排序数组中数的个数，返回的ans是一个list。    ans = []    i = 0    while i<num:        ans.append(random.randint(0, 10000))        i+=1    return ansdata = generateRandomData(7)print('randomData:',data)

1 冒泡排序

def bubbleSort(data):    '''    data为待排序的list    时间复杂度为n^2    '''    l = len(data)    for i in range(1, l):        for j in range(i, l)[::-1]:            if data[j-1] > data[j]:                data[j], data[j-1] = data[j-1], data[j]    return databubbleSort(data)print(data)

2 直接插入排序

def insertSort(data):    '''    时间复杂度为n^2    '''    l = len(data)    for i in range(1, l):        tmp = data[i]        while i>0:            if tmp >= data[i-1]:                break            data[i] = data[i-1]            i -= 1        data[i] = tmp    return datainsertSort(data)print(data)

3 希尔排序

def shellSort(data):    '''    时间复杂度为n^(3/2)    最后一次排序的增量需要为1    '''    l = len(data)    step = l // 2    while step > 0 :        for i in range(0, step):            '''            每个step里每个组，采用直接插入排序            '''            j = i + step            while j < l:                k = j - step                tmp = data[j]                while k >= 0:                    if tmp >= data[k]:                        break                    data[k+step] = data[k]                    k -= step                data[k+step] = tmp                j = j + step        step = step // 2shellSort(data)print(data)

4 计数排序

def countSort(data, l):    '''    时间复杂度为n    l为待排序数组中可能的最大值    需要额外空间    '''    l = l + 1    data_count = [0 for x in range(l)]    data_ans = [0 for x in range(len(data))]    for x in data:        data_count[x] = data_count[x] + 1    for i in range(1, l):        data_count[i] = data_count[i] + data_count[i-1]    for x in data:        data_ans[data_count[x]-1] = x        data_count[x] -= 1        # print(data_ans)    return data_ansprint(countSort(data, 10000))

5 堆排序

def heapAdjust(dlist, p, r):    '''    调整堆为大顶堆    '''    tempdata = dlist[p]    j = 2*p    while j <= r:        if j < r and dlist[j] < dlist[j+1]:            j += 1        if tempdata > dlist[j]:            break        dlist[p] = dlist[j]        p = j        j = 2 * p    dlist[p] = tempdatadef heapSort(data):    '''    1 无序堆改变为大顶堆    2 抽出最小的元素后 重新排成大顶堆    时间复杂度为nlgn    '''    l = len(data)    data.insert(0, 0)    for i in range(l//2, 0, -1):        heapAdjust(data, i, l)    for i in range(l, 0, -1):        data[1], data[i] = data[i], data[1]        heapAdjust(data, 1, i-1)    data.pop(0)    return dataheapSort(data)print(data)

6 归并排序

def merge(dlist1, p, q, r):    '''    merge the dlist1[p, q] and dlist2[q+1, r]    output dlist as the results of merge    this function use the additional memory    '''    l = len(dlist1)    sublist1 = dlist1[p: q+1]    sublist2 = dlist1[q+1: r+1]    sublist1.append(float('inf'))    sublist2.append(float('inf'))    p1 = 0    p2 = 0    for i in range(p, r+1):        if sublist1[p1] <= sublist2[p2]:            dlist1[i] = sublist1[p1]            p1 += 1        else:            dlist1[i] = sublist2[p2]            p2 += 1    del sublist1    del sublist2    return dlist1def msort(dlist, p, r):    if p == r:        return dlist    else:        q = (p + r)//2        msort(dlist, p, q)        msort(dlist, q+1, r)        merge(dlist, p, q, r)def mergeSort(data):    '''    时间复杂度为n+lgn    '''    l = len(data)    msort(data, 0, l-1)    return datamergeSort(data)print(data)

7 快速排序

def quickSortPartition(dlist, p, r):    i = p - 1    for j in range(p, r):        if dlist[j] >= dlist[r]:            continue        else:            i += 1            dlist[i], dlist[j] = dlist[j], dlist[i]    dlist[i+1], dlist[r] = dlist[r], dlist[i+1]    return i+1def qsort(dlist, p, r):    if p < r :        q = quickSortPartition(dlist, p, r)        qsort(dlist, p, q-1)        qsort(dlist, q+1, r)def quickSort(data):    '''    平均时间复杂度为nlgn    最坏时间复杂度为n^2    平均空间复杂度为lgn    '''    l = len(data)    qsort(data, 0, l-1)    return dataquickSort(data)print(data)