LeetCode-476. Number Complement-思路详解-C++

题目：

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: 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.

翻译

给定给一个正整数，输出其补码，补码的策略是按位取反。
注：
1，给定的数的范围在32位有符号整数
2，假设没有前导0.即5的二进制就是101。

思路

按位取反，即可。

代码

class Solution {    public:        int findComplement(int num) {            long int flag = 1;            long int res = 0;            while(flag && flag <= num){                int t = flag&num;                if(t == 0){                    res |= flag;                }                flag = flag << 1;            }            return res;        }    };