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Easy Bit Manipulation

Cloudera

2020-10-05

1009. Complement of Base 10 Integer

Question:

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: LeetCode Question 476

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;
    }
}

Using XOR(^) to compare with the largest value with current number of digits. It may have the integer overflow problem.

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