Problem:
Write a function that takes an unsigned integer and returns the number of ’1’ bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11’ has binary representation 00000000000000000000000000001011, so the function should return 3.

• 使用移位操作，每次将最后的最低位累加
• 我想说一模一样的代码，JavaC++的执行效率真的相差挺大

the Runetime is 10ms

the Runtime is 239ms