程序员必须掌握的十大排序算法（下）

'''希尔排序'''
def Shell_Sort(arr):
    # 设定步长,注意类型
    step = int(len(arr) / 2)
    while step > 0:
        for i in range(step, len(arr)):
            # 类似插入排序, 当前值与指定步长之前的值比较, 符合条件则交换位置
            while i >= step and arr[i - step] > arr[i]:
                arr[i], arr[i - step] = arr[i - step], arr[i]
                i -= step
        step = int(step / 2)
    return arr

arr = [29, 63, 41, 5, 62, 66, 57, 34, 94, 22]
result = Shell_Sort(arr)
print('result list: ', result)
# result list: [5, 22, 29, 34, 41, 57, 62, 63, 66, 94]

'''归并排序'''def Merge(left, right):
    arr = []
    i = j = 0
    while j < len(left) and  i < len(right):
        if left[j] < right[i]:
            arr.append(left[j])
            j += 1
        else:
            arr.append(right[i])
            i += 1
    if j == len(left):
        # right遍历完
        for k in right[i:]:
            arr.append(k)
    else:
        # left遍历完
        for k in left[j:]:
            arr.append(k)
    return arr

def Merge_Sort(arr):
    # 递归结束条件
    if len(arr) <= 1:
        return arr
    # 二分
    middle = len(arr) // 2
    left = Merge_Sort(arr[:middle])
    right = Merge_Sort(arr[middle:])
    # 合并
    return Merge(left, right)

arr = [27, 70, 34, 65, 9, 22, 47, 68, 21, 18]
result = Merge_Sort(arr)
print('result list: ', result)
# result list: [9, 18, 21, 22, 27, 34, 47, 65, 68, 70]

'''计数排序'''
def Count_Sort(arr):
    max_num = max(arr)
    min_num = min(arr)
    count_num = max_num - min_num + 1
    count_arr = [0 for i in range(count_num)]
    res = [0 for i in range(len(arr))]
    # 统计数字出现的次数
    for i in arr:
        count_arr[i - min_num] += 1
    # 统计前面有几个比自己小的数
    for j in range(1, count_num):
        count_arr[j] = count_arr[j] + count_arr[j - 1]
    # 遍历重组
    for k in range(len(arr)):
        res[count_arr[arr[k] - min_num] - 1] = arr[k]
        count_arr[arr[k] - min_num] -= 1
    return res

arr = [5, 10, 76, 55, 13, 79, 5, 49, 51, 65, 30, 5]
result = Count_Sort(arr)
print('result list: ', result)
# result list: [5, 5, 5, 10, 13, 30, 49, 51, 55, 65, 76, 79]

'''基数排序'''
def Radix_Sort(arr):
    max_num = max(arr)
    place = 0
    while 10 ** place <= max_num:
        # 创建桶
        buckets = [[] for _ in range(10)]
        # 分桶
        for item in arr:
            pos = item // 10 ** place % 10
            buckets[pos].append(item)
        j = 0
        for k in range(10):
            for num in buckets[k]:
                arr[j] = num
                j += 1
        place += 1
    return arr

arr = [31, 80, 42, 47, 35, 26, 10, 5, 51, 53]
result = Radix_Sort(arr)
print('result list: ', result)
# result list: [5, 10, 26, 31, 35, 42, 47, 51, 53, 80]

'''桶排序'''
def Bucket_Sort(arr):
    num = max(arr)
    # 列表置零
    pre_lst = [0] * num
    result = []
    for data in arr:
        pre_lst[data - 1] += 1
    i = 0
    while i < len(pre_lst): # 遍历生成的列表，从小到大
        j = 0
        while j < pre_lst[i]:
            result.append(i + 1)
            j += 1
        i += 1
    return result

arr = [26, 53, 83, 86, 5, 46, 5, 72, 21, 4, 75]
result = Bucket_Sort(arr)
print('result list: ', result)
# result list: [4, 5, 5, 21, 26, 46, 53, 72, 75, 83, 86]