算法-排序-python

冒泡排序

__author__ = 'hp'

def bubble_sort(li):
    "冒泡排序"
    n = len(li)
    for i in range(n-1):
        for j in range(n-1-i):
            if li[j]>li[j+1]:
                li[j],li[j+1] = li[j+1],li[j]

def bubble_sort1(li):
    "冒泡排序"

    n = len(li)
    for i in range(n-1,0,-1):
        for j in range(i):
            if li[j]>li[j+1]:
                li[j],li[j+1] = li[j+1],li[j]

# 优化
def bubble_sort2(li):
    n = len(li)
    for i in range(n-1):
        count = 0
        for j in range(n-1-i):
            if li[j]>li[j+1]:
                li[j],li[j+1] = li[j+1],li[j]
                count += 1
        # 如果已经有序，退出循环
        if count == 0:
            return

li = [4,3,2,1]
bubble_sort1(li)
print(li)

选择排序

__author__ = 'hp'
# 选择排序

def select_sort(li):
    n = len(li)
    for j in range(n-1):
        min_index = j #最小值位置
        for i in range(j+1,n): # i为右侧无序遍历
            if li[i] < li[min_index]:
                min_index = i
        if min_index != j:
            li[min_index],li[j] = li[j],li[min_index]




li = [4,3,2,2,6,1]
select_sort(li)
print(li)

插入排序

__author__ = 'hp'

# 从右边无序第一个插入左边的有序中
def insert_sort(li):
    n = len(li)
    for j in range(1,n):
        # 无序从位置j开始
        for i in range(j,0,-1):
            if li[i]< li[i-1]:
                li[i],li[i-1] = li[i-1],li[i]
            else:
                break


li = [4,3,8,4,5,9,11,2]
insert_sort(li)
print(li)

快速排序

def quick_sort(li,left,right):
    if left<right: # 至少要有两个元素
        mid = partition(li,left,right)
        quick_sort(li,left,mid-1)
        quick_sort(li,mid+1,right)


# 排出一个中间值，左边都比它小，右边都比它大
def partition(li, left, right):
    tmp = li[left] # tmp = li[0]=2 第一位拿出来当作中间值，第一位空出
    while left < right:
        while left < right and li[right]>=tmp: # 从右边找比tmp小的数
            right -= 1 # 右边一直比tmp大，不停左移动，直到碰到比tmp小的，退出循环
        li[left] = li[right] # 碰到比tmp小的数，扔回去左边的空位
        while left <right and li[left] <=tmp:
            left += 1
        li[right] = li[left]
    li[left] = tmp # 退出循环，left=right，放回tmp
    return left # 返回tmp的位置


if __name__ == "__main__":
    li = [2,3,1,2,3,4]
    quick_sort(li,0,5)
    print(li)

归并排序

# __author__ = 'hp'
#
# def merge(li,low,mid,high):
#     tmp = []
#     i = low
#     j = mid+1
#     while i<=mid and j<=high:
#         if li[i]<li[j]:
#             tmp.append(li[i])
#             i += 1
#         else:
#             tmp.append(li[j])
#             j += 1
#     while i<=mid:
#         tmp.append(li[i])
#         i += 1
#     while j<=high:
#         tmp.append(li[j])
#         j += 1
#     li[low:high+1] = tmp
#
#
#
#
# def merge_sort(li,low,high):
#     if low < high:
#         mid = (low+high)//2
#         merge_sort(li,low,mid)
#         merge_sort(li,mid+1,high)
#         merge(li,low,mid,high)
#
#
# if __name__ == "__main__":
#     l1 = list(range(10))
#     import random
#     random.shuffle(l1)
#     merge_sort(l1,0,len(l1)-1)
#     print(l1)



# merge排序

def merge(li,left,mid,right):
    i = left
    j = mid+1
    tmp =[]
    while i<=mid and j<=right:
        if li[i]<=li[j]:
            tmp.append(li[i])
            i += 1
        else:
            tmp.append(li[j])
            j += 1
    while i<=mid:
        tmp.append(li[i])
        i += 1
    while j<=right:
        tmp.append(li[j])
        j += 1
    li[left:right+1] = tmp

def merge_sort(li,left,right):
    if left<right:
        mid = (left+right)//2
        merge_sort(li,left,mid)
        merge_sort(li,mid+1,right)
        merge(li,left,mid,right)


li = [1,3,2,4,7,5] 

merge_sort(li,0,len(li)-1)
print(li)

来源：CSDN

作者：weixin_38892128

链接：https://blog.csdn.net/weixin_38892128/article/details/104126284