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
My Solution
To solve this problem, we just AND n with 1 and add that to our running count. We then right shift by 1 to move onto the next bit.
Time complexity would be O(1) because we deal with a constant number of 32 bits for any number n within the constraints. Space complexity would be O(1) since we only require constant extra space.
class Solution {
public int hammingWeight(int n) {
int count = 0;
while (n > 0) {
count += (n & 1);
n >>= 1;
}
return count;
}
}