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
Solution: Bit
Find the smallest binary number c that is all 1s, (e.g. “111”, “11111”) that is greater or equal to N.
ans = C ^ N or C – N
Time complexity: O(log(n))
Space complexity: O(1)
C++
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// Author: Huahua, running time: 4 ms, 8 MB class Solution { public: int bitwiseComplement(int N) { int c = 1; while (c < N) c = (c << 1) | 1; return N ^ c; } }; |
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