list 拓展 二分法 创建一个函数查找

#  二分查找
l01 = [i for i in range(1,101)]
start_index = 0
end_index = len(l01)-1
while start_index <= end_index:
     mid_index = (start_index + end_index) // 2
     if l01[mid_index] == 77:
         print('找到了')
         break
     elif l01[mid_index] > 77:
         end_index = mid_index - 1
     else:
         start_index = mid_index + 1
 else:
     print('没找到')
#  找到了


#      binarysearch    创建一个函数 查找 是否存在

def binarysearch(l01,num):
     start_index = 0
     end_index = len(l01) - 1
     while start_index <= end_index:
         mid_index = (start_index + end_index) // 2
         if l01[mid_index] == num:
             return mid_index
         elif l01[mid_index] > num:
             end_index = mid_index - 1
         else:
             start_index = mid_index + 1
     return  -1
print(binarysearch([1,2,3,5,4,5,6,9,84,5,2,5,874,5,5],84))
#  -1

#     寻找中间数是否对应 对应输出 84 不对应输出-1