[leetcode]191.Number of 1 Bits

题目

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

Example:

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

解法

思路

这道题和leetcode]190.Reverse Bits一样，都是关于位运算的题目，思路很简单，用countOne来计数，如果n的最后一位是1，则countOne加一。然后将n右移一位。

代码

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