191. Number of 1 Bits
Write a function that takes an unsigned integer and returns the number of '1' bits it has (also known as the Hamming weight).
Note:
- Note that in some languages such as Java, there is no unsigned integer type. In this case, the input will be given as a signed integer type. It should not affect your implementation, as the integer's internal binary representation 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
.
Follow up: If this function is called many times, how would you optimize it?
Example 1:
Input: n = 00000000000000000000000000001011 Output: 3 Explanation: The input binary string 00000000000000000000000000001011 has a total of three '1' bits.
Example 2:
Input: n = 00000000000000000000000010000000 Output: 1 Explanation: The input binary string 00000000000000000000000010000000 has a total of one '1' bit.
Example 3:
Input: n = 11111111111111111111111111111101 Output: 31 Explanation: The input binary string 11111111111111111111111111111101 has a total of thirty one '1' bits.
Constraints:
- The input must be a binary string of length
32
Rust Solution
#![allow(clippy::unreadable_literal)]
struct Solution;
impl Solution {
#[allow(non_snake_case)]
fn hammingWeight(n: u32) -> i32 {
n.count_ones() as i32
}
}
#[test]
fn test() {
let n = 0b00000000000000000000000000001011;
let res = 3;
assert_eq!(Solution::hammingWeight(n), res);
let n = 0b00000000000000000000000010000000;
let res = 1;
assert_eq!(Solution::hammingWeight(n), res);
let n = 0b11111111111111111111111111111101;
let res = 31;
assert_eq!(Solution::hammingWeight(n), res);
}
Having problems with this solution? Click here to submit an issue on github.