LeetCode 简单操作 | 476. Number Complement

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本文介绍了解决LeetCode题目476.数字的补数的方法。该题要求输入一个正整数，输出其二进制表示的按位取反结果。文章提供了两种解决方案：一种是通过循环左移并检查最高位来逐位构造补数；另一种则是利用掩码技巧高效完成取反操作。

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/*
 * Leetcode476. Number Complement
 * Funtion: 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: Input:  5(101)
            Output: 2(010)
 * Author: LKJ
 * Date: 2017/3/02
 * Hint:
*/
#include <iostream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>

using namespace std;

class Solution {
public:
    int findComplement(int num) {
        int i = 0,res = 0;
        while((!(num&0x80000000))&&(i<31)){num <<= 1;i++;}
        while(i<32){
            res <<= 1;
            res |= ((num&0x80000000)==0) ? 1 : 0;
            i++;
            num<<=1;
        }
        return res;
    }
};

/*function2
class Solution {
public:
    int findComplement(int num) {
        unsigned mask = ~0;
        while (num & mask) mask <<= 1;
        return ~mask & ~num;
    }
};

//num          = 00000101
//mask         = 11111000
//~mask & ~num = 00000010

*/


int main(){
    int myin = 0;
    int myout;
    Solution SA;

    myout = SA.findComplement(myin);
    cout << myout << endl;

    return 0;
}