(Leet Code c++)Number of 1 Bits

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, the input represents the signed integer. -3.

 

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.

 

n이 0이 될 때까지 1의 개수를 세어주도록 한다.

n과 1을 and(&)연산을 통해 1인지 아닌지 확인한다.

1이라면 answer++을 해주면 된다.

마지막에는 left shift 연산을 이용해 n을 줄여주면 된다.

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int answer = 0;
        
        while(n > 0){
            if(n & 1){
                answer++;
            }
            n >>= 1;
        }
        
        return answer;
    }
};