Coding tips：5种常见的排序

def bubble_sort(a):
    for i in range(len(a)):
        for j in range(len(a)-i-1):  # 将最小的排到最后面
            if(a[j]>a[j+1]):
                a[j], a[j+1] = a[j+1],a[j]
    return(a)


def select_sort(a):
    for i in range(len(a)): # 排序的次数
        temp = i  # 记录最小元素对应的下标
        # 从待排元素中挑选最小值对应的下标temp
        for j in range(i+1,len(a)):
            if(a[temp]>a[j]):
                temp = j
        a[i],a[temp] = a[temp],a[i]
    return a


def insert_sort(a):
    for i in range(1,len(a)):
        temp = a[i] # 待插入的元素
        # 向前面有序的数组a[0:j]中插入新元素a[i]：寻找插入的位置，找到后再插入
        j = i-1
        while j>=0 and temp<a[j]:
            a[j+1] = a[j]
            j=j-1
        # 由于j-1导致的不满足，此处要恢复为正常值j+1，将新元素插入合适的位置j+1
        a[j+1] = temp
    return a

    # # 遍历待插入的元素
    # for i in range(1,len(a)):
    #     # 向有序的数组中a[0:j]插入新元素a[i]：边比较边交换值
    #     for j in range(i,0,-1):
    #         # 通过两两比较，将a[i]插入合适的位置：比一个，换一个
    #         if(a[j]<a[j-1]):
    #             a[j-1],a[j] = a[j],a[j-1]
    # return a

# 快速排序：
# 1遍历一遍数组将记录分成两部分：左面比pivot小，右面比pivot大，原地交换
def partition(a,left,right):
    i = left
    j = right
    pivot = a[left]
    while i<j:
        # 下面两个while的顺序不能调换
        while (i < j and a[j] >= pivot):
            j = j - 1
        a[i] = a[j]
        while(i<j and a[i]<pivot):
            i=i+1
        a[j] = a[i]
    a[i] = pivot
    return i

# 2快速排序
def quick_sort(a,left,right):
    if(left<right):
        p = partition(a,left,right)
        quick_sort(a,left,p-1)  # 对左边的元素排序
        quick_sort(a,p+1,right)  # 对右边的元素排序
    return a

# 合并排序(归并排序)
# 1合并左右两个部分
def merge(left,right):  # 将两个数组合并为一个数组
    l,r = 0,0
    result = []
    while l<len(left) and r<len(right):
        if(left[l]<right[r]):
            result.append(left[l])
            l = l+1
        else:
            result.append(right[r])
            r = r+1
    result = result+left[l:]
    result = result+right[r:]
    return result

# 2合并排序
def merge_sort(a):
    if(len(a)<2):
        return a
    mid = len(a)//2
    left = merge_sort(a[:mid])
    right = merge_sort(a[mid:])
    return merge(left,right)

a = [2,3,1,4,7,5,6,9,8]
# bubble_a = bubble_sort(a)
# select_a = select_sort(a)
# insert_a = insert_sort(a)
# quick_a = quick_sort(a,0,len(a)-1)
# merge_a = merge_sort(a)