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

Example 1:

Input: 11
Output: 3
Explanation: Integer 11 has binary representation 00000000000000000000000000001011 

Example 2:

Input: 128
Output: 1
Explanation: Integer 128 has binary representation 00000000000000000000000010000000
 

題意：計算一個無符號整數二進位制表示中1的數量；

解法：最容易想到的自然就是通過計算其二進位制表示來統計1的數量；不過，這裡我們可以考慮使用位操作，首先我們每次將整數右移一位後再與1相與，判斷結果是否為1即可計算整數二進位制表示特定位上是否為1；

Java

public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int result = 0;
        for (int i = 0; i < 32; i++) {
            result = ((n >> i) & 0x01) == 1 ? result + 1 : result; 
        }
        return result;
    }
}