LeetCode-in-Java
191. Number of 1 Bits
Easy
Given a positive integer n, write a function that returns the number of set bits in its binary representation (also known as the Hamming weight).
Example 1:
Input: n = 11
Output: 3
Explanation:
The input binary string 1011 has a total of three set bits.
Example 2:
Input: n = 128
Output: 1
Explanation:
The input binary string 10000000 has a total of one set bit.
Example 3:
Input: n = 2147483645
Output: 30
Explanation:
The input binary string 1111111111111111111111111111101 has a total of thirty set bits.
Constraints:
1 <= n <= 231 - 1
Follow up: If this function is called many times, how would you optimize it?
Solution
public class Solution {
public int hammingWeight(int n) {
int sum = 0;
boolean flag = false;
if (n < 0) {
flag = true;
n = n - Integer.MIN_VALUE;
}
while (n > 0) {
int k = n % 2;
sum += k;
n /= 2;
}
return flag ? sum + 1 : sum;
}
}