Complement of Base 10 Integer

Complement of Base 10 Integer

Every non-negative integer N has a binary representation. For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on. Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a 0 and 0 to a 1. For example, the complement of "101" in binary is "010" in binary.

For a given number N in base-10, return the complement of it's binary representation as a base-10 integer.

Example 1:

Input: 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.

Example 2:

Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.

Example 3:

Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.

Note:

1. 0 <= N < 10^9

2. This question is the same as 476: https://leetcode.com/problems/number-complement/

Solutions

🧠 Cpp

class Solution
{
public:
    //O(1) solution
    int bitwiseComplement(int N)
    {
        if(N == 0)
            return 1;
        //leading_zeros
        const size_t LZ =  __builtin_clz(N); 
        return (~(N << LZ)) >> LZ;
    }
};