128th LeetCode Weekly Contest Complement of Base 10 Integer

Every non-negative integer N has a binary representation.  For example, 5 can be represented as "101" in binary, 11 as "1011" in binary, and so on.  Note that except for N = 0, there are no leading zeroes in any binary representation.

The complement of a binary representation is the number in binary you get when changing every 1 to a 0 and 0 to a 1.  For example, the complement of "101" in binary is "010" in binary.

For a given number N in base-10, return the complement of it's binary representation as a base-10 integer.

Example 1:

Input: 5
Output: 2
Explanation: 5 is "101" in binary, with complement "010" in binary, which is 2 in base-10.

Example 2:

Input: 7
Output: 0
Explanation: 7 is "111" in binary, with complement "000" in binary, which is 0 in base-10.

Example 3:

Input: 10
Output: 5
Explanation: 10 is "1010" in binary, with complement "0101" in binary, which is 5 in base-10.

Note:

1. 0 <= N < 10^9

题意啥的去看看中文版的就好了。简单一点看看example

大佬的代码很短的

class Solution {
public:
    int bitwiseComplement(int N) {
        int num[33] = {0};
        int cnt = 0;
        int sum = 0;
        int flag = 1;
        if(N == 0){
            return 1;
        }
        while(N){
            int pos = N % 2;
            num[cnt++] = pos == 1 ? 0 : 1;
            N/=2;
        }
        for(int i = 0 ; i < cnt ; i++){
            //cout<<num[i]<<endl;
            if(num[i] == 0){
                sum += 0;
            }else{
                sum += flag;                
            }
            flag *= 2;
        }
        //cout<<endl;
        return sum;
    }
};