二进制搜索算法python在列表中找不到0个索引成员

Question

[请帮助改善代码-算法会在所有情况下都找到搜索到的数字，但当您尝试找到0索引编号或在我的情况下search_num = 1时除外。

list1 = [1, 3, 4, 5, 19, 21, 52, 100, 152]
search_num = 1

def binarySearch(array, number):

    lower_b_index = 0
    upper_b_index = len(array) - 1

    while lower_b_index <= upper_b_index:

        mid_point = (lower_b_index + upper_b_index) // 2

        if array[mid_point] == number:
            return mid_point
        elif array[lower_b_index] == number:
            return lower_b_index
        else:
            if array[mid_point] < number:
                lower_b_index = mid_point + 1
            else: 
                upper_b_index = mid_point - 1 

    return False

a1 = binarySearch(list1, search_num)

if a1:
    print("The searched position: ", a1 + 1)
else:
    print("Not Found!")

Answer 1

您的问题不在您的binarySearch算法中，而是在您的if语句之后。

您算法返回正确的a1 = 0，并且您检查的if 0和0的布尔值为False [>]

一个简单的解决方法是return None并检查if a1 is not None

list1 = [1, 3, 4, 5, 19, 21, 52, 100, 152]
search_num = 1

def binarySearch(array, number):

    lower_b_index = 0
    upper_b_index = len(array) - 1

    while lower_b_index <= upper_b_index:

        mid_point = (lower_b_index + upper_b_index) // 2

        if array[mid_point] == number:
            return mid_point
        elif array[lower_b_index] == number:
            return lower_b_index
        else:
            if array[mid_point] < number:
                lower_b_index = mid_point + 1
            else: 
                upper_b_index = mid_point - 1 

    return None  # Change here

a1 = binarySearch(list1, search_num)

if a1 is not None:  # Change here
    print("The searched position: ", a1 + 1)
else:
    print("Not Found!")