191. Number of 1 Bits

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.

思路：再判斷數字是否是2的次方，有個方式是 n&(n-1) ，他會把數字最後一個 1 的bit去掉，那我們可以不斷用這方式，看要去掉多少次1會把數字變成0

class Solution {
public:
int hammingWeight(uint32_t n) {
int count = 0;
while(n !=0) {
n = n & (n-1);
count++;
}

return count;
}
};