[LeetCode] Problem 476 - Number Complement

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Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note

  1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
  2. You could assume no leading zero bit in the integer’s binary representation.

Example

No.1

Input: 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.

No.2

Input: 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.

Code

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public int findComplement(int num) {
    int mask = ~0;

    while ((num & mask) != 0)
        mask <<= 1;

    return ~num ^ mask;
}