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.
给定一个unsigned integer数，返回bit值为1的个数
算法分析
方法一
将给定数值与1做“与”运算，即可得到结果
Java代码
public class Solution {
// you need to treat n as an unsigned value
public int hammingWeight(int n) {
int count = 0;
int mask = 1;
for (int i = 0; i < 32; i ++) {
if ((n & mask) != 0) {
count ++;
}
mask = mask << 1;
}
return count;
}
}
方法二
如图1所示，n & (n - 1)运算
Paste_Image.png
Java代码
public class Solution {
// you need to treat n as an unsigned value
public int hammingWeight(int n) {
int sum = 0;
while (n != 0) {
sum ++;
n &= (n - 1);
}
return sum;
}
}
