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：因为是32位的，循环32次，n&1==1时，count++，n>>1;

代码如下(已通过leetcode)

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
       String str=Integer.toBinaryString(n);
//System.out.println(str);
       int count=0;
       for(int i=0;i<str.length();i++) {
        if(str.charAt(i)=='1') count++;
       }
       return count;
   
    }
}