LeetCode 1012 - Complement of Base 10 Integer

https://leetcode.com/problems/complement-of-base-10-integer/

Every non-negative integer N has a binary representation.  For example, 5 can be represented as "101" in binary, 11as "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

https://leetcode.com/problems/complement-of-base-10-integer/discuss/256740/JavaC%2B%2BPython-Find-111.....1111-greater-N
O(logN) Time

Let's find the first number X that X = 1111....1 >= N
And also, it has to be noticed that,
N = 0 is a corner case expecting1 as result.

Solution 1:

N + bitwiseComplement(N) = 11....11 = X
Then bitwiseComplement(N) = X - N

    public int bitwiseComplement(int N) {
        int X = 1;
        while (N > X) X = X * 2 + 1;
        return X - N;
    }

N ^ bitwiseComplement(N) = 11....11 = X
bitwiseComplement(N) = N ^ X

    public int bitwiseComplement(int N) {
        int X = 1;
        while (N > X) X = X * 2 + 1;
        return N ^ X;
    }

public int bitwiseComplement(int n) {
    return n != 0 ? n ^ (Integer.highestOneBit(n) << 1) - 1 : 1;
}

https://leetcode.com/problems/complement-of-base-10-integer/discuss/256741/Simple-Java-Sol-(XOR)

    public int bitwiseComplement(int N) {
        // Find number of bits in the given integer
        int bitCount = (int) Math.floor(Math.log(N)/Math.log(2))+1;

        // XOR the given integer with math.pow(2,bitCount-1)
        return ((1 << bitCount) - 1) ^ N;
    }

https://leetcode.com/problems/complement-of-base-10-integer/discuss/257022/Java-simple-1-line-bit-manipulation-(left-and-right-shifts)-0ms

Just actually do the complement operation ~, after first shifting away all the leading zeroes, and then shift away all the trailing ones.

    public int bitwiseComplement(int N) {
        return (N==0) ? 1 : (~(N<<(N=Integer.numberOfLeadingZeros(N))))>>N;
    }

X.
https://leetcode.com/problems/complement-of-base-10-integer/discuss/256770/JavaPython-1-line-cheat

Swap 0 and 1 in the binary string.

    public int bitwiseComplement(int N) {
        return Integer.parseInt(Integer.toBinaryString(N).replace('0', '2').replace('1', '0').replace('2', '1'), 2);
    }