1012

1012. Complement of Base 10 Integer (Easy)

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

Companies:
Cloudera

Related Topics:
Math

Solution 1.

// OJ: https://leetcode.com/problems/complement-of-base-10-integer/
// Author: github.com/lzl124631x
// Time: O(1)
// Space: O(1)
class Solution {
public:
    int bitwiseComplement(int N) {
        if (!N) return 1;
        unsigned mask = ~0;
        while (mask & N) mask <<= 1;
        return ~N & ~mask;
    }
};