Easy Bit Manipulation

Cloudera

2020-10-03

476. Number Complement

Question:

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

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:

• The given integer num is guaranteed to fit within the range of a 32-bit signed integer.
• num >= 1
• You could assume no leading zero bit in the integer’s binary representation.
• This question is the same as 1009: LeetCode Question 1009

Solution:

Using XOR(^) to compare each digit with 1.

class Solution {
    public int bitwiseComplement(int N) {
        if (N == 0) return 1;
        if (N == 1) return 0;
        int orBit = 1;
        int rest = N;
        while (rest != 0) {
            N ^= orBit;
            orBit <<= 1;
            rest >>= 1;
        }
        return N;
    }
}