def erfenchazhao (num,shu):
    n =len(shu)
    max_index,min_index = n-1,0
    while min_index  <= max_index :
        mid =(max_index+min_index)//2
        if shu[mid] ==num :
            return mid
        elif shu[mid] > num :
             max_index = mid-1

        else:
            min_index = mid+1
    return -1

array = [2,5,7,9,14,45]
num  = 7

weizi =erfenchazhao(num,array)
if weizi != -1 :
    print("该目标元素在数组中，下标为:",weizi)
else:
    print("该目标元素不在数组中")