C 的位操作

位操作运算符

C++基本的位操作符有与、或、异或、取反、左移、右移这6种，它们的运算规则如下所示：

Note:

• 位操作只能用于整形数据，对float和double类型进行位操作会被编译器报错。
• 位操作符的运算优先级比较低，因为尽量使用括号来确保运算顺序，否则很可能会得到莫明其妙的结果
• 另外位操作还有一些复合操作符，如&=、|=、 ^=、<<=、>>=

位操作实战

476. Number Complement Given a positive integer, output its complement number. The complement strategy is to flip the bits of its 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.

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.
3. This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/

题目来源:https://leetcode.com/problems/number-complement/

class Solution {
public:
    int findComplement(int num) {
        int tmp = num;
        int mask = 0;
        while (tmp)
        {
            mask = mask << 1;
            mask = mask | 1;
            tmp = tmp >> 1;
        }
        int result = (~num) & mask;
        return result;
    }
};