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.

题目：求32bit二进制数中1的个数.

1.int转为32bit二进制数

2.toBinaryString然后，count

public class Solution {
// you need to treat n as an unsigned value
public int hammingWeight(int n) {

Integer num = new Integer(n);
String s = num.toBinaryString(n);
System.out.println(s);
int count=0;
for(int i =0;i<s.length();i++){
if(s.charAt(i)=='1'){
count++;
//    System.out.println(count);
}
}

return count;
}
}

248ms.