3 - 排序算法

一、插入排序

1、直接插入排序

# -*- coding: utf-8 -*-

def InsertSort(List):    
    # 获取列表长度
    length = len(List)
    for i in range(1, length):    #i代表每一轮的当前值，j代表当前值的前一个值
        j = i - 1
        # 如果当前值小于前一个元素,则将当前值作为一个临时变量存储,将前一个元素后移一位
        if (List[i] < List[j]):
            temp = List[i]
            List[i] = List[j]
            # 继续往前寻找,如果有比临时变量大的数字,则后移一位,直到找到比临时变量小的元素或者达到列表第一个元素
            j = j - 1
            while j >= 0 and List[j] > temp:
                List[j + 1] = List[j]
                j = j - 1
            # 将临时变量赋值给合适位置
            List[j + 1] = temp
List = [49, 38, 65, 97, 76, 13, 27, 49]
InsertSort(List)
print(List)

2、折半插入排序

二、希尔排序

def ShellInsetSort(array, len_array, dk):

    for i in range(dk, len_array):  # 从下标为dk的数进行直接插入排序
        position = i
        current_val = array[position]  # 要插入的数

        index = i
        j = int(index / dk)  # index与dk的商
        index = index - j * dk

        # while True:  # 找到第一个的下标，在增量为dk中，第一个的下标index必然 0<=index<dk
        #     index = index - dk
        #     if 0<=index and index <dk:
        #         break


        # position>index,要插入的数的下标必须得大于第一个下标
        while position > index and current_val < array[position-dk]:
            array[position] = array[position-dk]  # 往后移动
            position = position-dk
        else:
            array[position] = current_val


def ShellSort(array, len_array):  # 希尔排序
    dk = int(len_array/2)  # 增量
    while(dk >= 1):
        ShellInsetSort(array, len_array, dk)
        print(">>:",array)
        dk = int(dk/2)

if __name__ == "__main__":
    array = [49, 38, 65, 97, 76, 13, 27, 49, 55, 4]
    print(">:", array)
    ShellSort(array, len(array))

三、冒泡排序

list = [1, 2, 3, 4, 5, 6]

for t in range(len(list)-1):

    for i in range(0, len(list)-1):
        tmp = list[i]
        if list[i] < list[i+1]:
            list[i] = list[i+1]
            list[i+1] =tmp

print(list)

四、快速排序 

def sub_sort(array,low,high):  # 实现分组
    key = array[low]
    while low < high:
        while low < high and array[high] >= key:
            high -= 1
        while low < high and array[high] < key:
            array[low] = array[high]
            low += 1
            array[high] = array[low]
    array[low] = key
    return low


def quick_sort(array,low,high):
     if low < high:
        key_index = sub_sort(array,low,high)
        quick_sort(array,low,key_index)
        quick_sort(array,key_index+1,high)


if __name__ == '__main__':
    array = [8,10,9,6,4,16,5,13,26,18,2,45,34,23,1,7,3]
    print(array)
    quick_sort(array,0,len(array)-1)
    print(array)

五、选择排序 

def selectedSort(myList):
    #获取list的长度
    length = len(myList)
    #一共进行多少轮比较
    for i in range(0,length-1):
        #默认设置最小值得index为当前值
        smallest = i
        #用当先最小index的值分别与后面的值进行比较,以便获取最小index
        for j in range(i+1,length):
            #如果找到比当前值小的index,则进行两值交换
            if myList[j]<myList[smallest]:
                tmp = myList[j]
                myList[j] = myList[smallest]
                myList[smallest]=tmp
        #打印每一轮比较好的列表
        print("Round ",i,": ",myList)

myList = [1,4,5,0,6]
print("Selected Sort: ")
selectedSort(myList)

六、堆排序

暂时不做实现

七、归并排序

 

def merge(a, b):
    c = []
    h = j = 0
    while j < len(a) and h < len(b):
        if a[j] < b[h]:
            c.append(a[j])
            j += 1
        else:
            c.append(b[h])
            h += 1

    if j == len(a):
        for i in b[h:]:
            c.append(i)
    else:
        for i in a[j:]:
            c.append(i)

    return c


def merge_sort(lists):
    if len(lists) <= 1:
        return lists
    middle = int(len(lists)/2)
    left = merge_sort(lists[:middle])
    right = merge_sort(lists[middle:])
    return merge(left, right)


if __name__ == '__main__':
    a = [4, 7, 8, 3, 5, 9]
    print(merge_sort(a))

八、基数排序

def radix_sort(s):
    """基数排序"""
    i = 0 # 记录当前正在排拿一位，最低位为1
    max_num = max(s)  # 最大值
    j = len(str(max_num))  # 记录最大值的位数
    while i < j:
        bucket_list =[[] for _ in range(10)] #初始化桶数组
        for x in s:
            bucket_list[int(x / (10**i)) % 10].append(x) # 找到位置放入桶数组
        print(bucket_list)
        s.clear()
        for x in bucket_list:   # 放回原序列
            for y in x:
                s.append(y)
        i += 1

if __name__ == '__main__':
    a = [51,7,12,336,2,67,16,16,553]
    radix_sort(a)
    print(a)

 

认真理解排序算法思想，然后编码实现，排序算法是灵魂！