python二分查找算法/冒泡排序,及快速排序

二分查找算法

l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88]

你觀察這個列表，這是否是一個從小到大排序的有序列表呀？

若是這樣，假如我要找的數比列表中間的數還大，是否是我直接在列表的後半邊找就好了？

 

 

這就是二分查找算法！

那麼落實到代碼上咱們應該怎麼實現呢？ 

二分法

l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88]

def func(num_list,aim,start=0,end=None):
    end=len(num_list)-1 if end is None else end
    print(end)
    mid_index=(end-start)//2+start
    print(mid_index)
    if start <= end:
        if num_list[mid_index] > aim:
            func(num_list,aim,start=start,end=mid_index-1)
        elif num_list[mid_index] < aim:
            func(num_list,aim,start=mid_index+1,end=end)
        else:
            print('找到了{},下標爲{},從左數第{}個數'.format(aim,mid_index,mid_index+1))
    else:
        print('不存在')

func(l,72,0,)

 

二分法

def search(num,l,start=None,end=None):
    start = start if start else 0
    end = end if end is not None else len(l) - 1
    mid = (end - start)//2 + start
    if start > end:
        return None
    elif l[mid] > num :
        return search(num,l,start,mid-1)
    elif l[mid] < num:
        return search(num,l,mid+1,end)
    elif l[mid] == num:
        return mid

l = [2,3,5,10,15,16,18,22,26,30,32,35,41,42,43,55,56,66,67,69,72,76,82,83,88]

print(search(55,l,))

 冒泡排序

#冒泡排序
def sort_maopao(num_list):
    #開始排序
    for i in range(len(num_list)):
        for j in range(i,len(num_list)):
            if num_list[i]>num_list[j]:
                num_list[i],num_list[j]=num_list[j],num_list[i]
    return num_list

 快速排序

def quick_sort(num_list):
    if not num_list or len(num_list)<=1:
        return num_list
    mid=num_list[0]
    left=quick_sort([i for i in num_list[1:] if i < mid])
    right=quick_sort([i for i in num_list[1:] if i >=mid])
    return left+[mid]+right