Number Complement[E,Bit Manipulation]

https://leetcode.com/problems/number-complement/description/?envType=daily-question&envId=2024-08-22

The complement of an integer is the integer you get when you flip all the 0's to 1's and all the 1's to 0's in its binary representation.

• For example, The integer 5 is "101" in binary and its complement is "010" which is the integer 2.

Given an integer num, return its complement.

 

Example 1:

Input: num = 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

Example 2:

Input: num = 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

 

Constraints:

• 1 <= num < 231

bit단위의 계산을 하는 문제는 처음이라 난해하다.

 

1. C

int findComplement(int num) {
    unsigned int mask = ~0;
    while(num & mask){
        mask <<=1;
    }

    return ~mask & ~num;
}

 

2. Python

class Solution:
    def findComplement(self, num: int) -> int:
        bit_length = num.bit_length()
        
        mask = (1 << bit_length) - 1
        
        return num ^ mask

 

내가 주로 다룰 범위는 아닌 거 같다.

bit 영역은 일단 pass하는 걸로..