1009. 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:

0 <= N < 10^9
This question is the same as 476: https://leetcode.com/problems/number-complement/

这题主要就是求补码的结果，所以很直接，我们首先找到最接近的bit位都为1的值，然后减去该N即可。

class ComplementOfBase10Integer : public Solution {
public:
  void Exec() {}

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