写一个以整数为输入的函数， 并返回二进制中等于1的位的数目

题目描述：

# Write a function that takes an integer as input,
# and returns the number of bits that are equal to one in the binary
# representation of that number. You can guarantee that input is non-negative.
#
# Example: The binary representation of 1234 is 10011010010,
# so the function should return 5 in this case


我的解答：

def countBits(a):
    b = bin(abs(a)).replace('0b', "")    # python 自带了方法 bin 函数，比如 bin(12345) 回返回字符串 '0b11000000111001', 这个时候在把0b去掉即可
    return b.count("1")


网上解法：

def countBits(a):
    return bin(a).count("1")