二分法查找-Python版

def binary_search(list, item):
    low = 0  # (以下2行）low和high用于跟踪要在其中查找的列表部分
    high = len(list) - 1
    n = 0
    while low <= high:  # 只要范围没有缩小到只包含一个元素
        n += 1
        mid_1 = (low + high)/2  # 就检查中间的元素
        mid = int(mid_1)
        guess = list[mid]
        if guess == item:  # 找到了元素
            return "要猜的数字在列表中的索引号为%d，共猜了%d次"%(mid,n)
        if guess > item:  # 猜的数字大了
            high = mid -1
        else:  # 猜的数字小了
            low = mid + 1
    return "没有这个数"  # 没有指定的元素


my_list = []
for i in range(1, 201):
    my_list.append(i)
print(my_list)

print(binary_search(my_list, 100))
print(binary_search(my_list, 111))

#运行结果

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200]
要猜的数字在列表中的索引号为99，共猜了1次
要猜的数字在列表中的索引号为110，共猜了8次

Process finished with exit code 0