binary

def bin(number:int) -> str:
    if number == 0:
        return '0b0'
    is_negative = number < 0
    number = abs(number)
    res = []

    while number > 0:
        # res.append(str(number % 2))
        i = str(number % 2)  # 取余数
        print(i)
        # number //= 2
        res.append(str(number & 1))  # 取最低位
        number >>= 1  # 右移一位

    res.reverse()
    binary = ''.join(res)

    if is_negative:
        return '-0b' + binary
    return '0b' + binary

combinatorics