问题描述
Write a function that takes an unsigned integer and return the number of ‘1’ bits it has (also known as the Hamming weight).
Example 1:
Input: 00000000000000000000000000001011
Output: 3
Explanation: The input binary string 00000000000000000000000000001011 has a total of three ‘1’ bits.
Example 2:
Input: 00000000000000000000000010000000
Output: 1
Explanation: The input binary string 00000000000000000000000010000000 has a total of one ‘1’ bit.
Example 3:
Input: 11111111111111111111111111111101
Output: 31
Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one ‘1’ bits.
Note:
Note that in some languages such as Java, there is no unsigned integer type. In this case, the input will be given as signed integer type and should not affect your implementation, as the internal binary representation of the integer is the same whether it is signed or unsigned.
In Java, the compiler represents the signed integers using 2’s complement notation. Therefore, in Example 3 above the input represents the signed integer -3.
解决思路
将原数按位&1，并且用flag标记下运算结果为1的时候，用记录数计数，最终计数器的值即为1的个数
问题解惑
按位&1的作用？ 任何数&1是这个数本身，0&1为0,1&1为1，所以可以用来标记1。
代码
package leetcode;
public class Numberof1Bits {
public int hammingWeight(int n) {
int flag = 0;
int count = 0;
for(int i = 0; i < 32; i++){
flag = n & 1;
if(flag == 1){
count++;
}
n = n >> 1;
}
return count;
}
}
