# LeetCode #476 Number Complement 数字的补数

19℃

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

Note:
The given integer is guaranteed to fit within the range of a 32-bit signed integer.
You could assume no leading zero bit in the integer’s binary representation.

Example:
Example 1:
Input: 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: 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.

e.g. 5 -> 0x101 -> mask = 2 ^ 3 – 1 = 0x111 -> return 010

C++:

class Solution {
public:
int findComplement(int num) {
int i = 1;
while (i < num) {
i <<= 1;
i++;
}
return (i ^ num);
}
};


Java:

class Solution {
public int findComplement(int num) {
for (int i = 0; i < 32; i++) if (num < (1 << (i + 1))) return (1 << (i + 1)) - 1 - num;
return Integer.MAX_VALUE - num;
}
}


Python:

class Solution:
def findComplement(self, num: int) -> int:
return num ^ int((len(bin(num)) - 2) * '1', 2)