LeetCode(Others)Number of 1 Bits

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).

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

思路：求二进制表示中1的个数，只要获得二进制表示再统计其中1的个数即可，利用Integer.toBinaryString()的方法可以解决。

代码如下：

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

还有一种按位与的思路也很不错，贴下代码：

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++){
            if((n&1)==1){
                result++;
            }
            n=n>>>1;
        }
        return result;
    }
}