leetcode.476. Number Complement

Question

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

Note:

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

Example 1:

Input: 5Output: 2Explanation: 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: 1Output: 0Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

Solution

获取num的最大位的数值Tmax，取num与Tmax的异或，即补码。

int findComplement(int num) {    int mask = num;    mask |= mask >> 1;    mask |= mask >> 2;    mask |= mask >> 4;    mask |= mask >> 8;    mask |= mask >> 16;    return mask ^ num;}