The problem link is problem 191
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.
We can use n&(n-1) to test if a int is power of 2,n&=(n-1) will remove the lowest 1 bit.
public int hammingWeight(int n) {
int ret = 0;
while (n != 0) {
n &= n - 1;
ret++;
}
return ret;
}