1009. Complement of Base 10 Integer.cpp

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:

0 <= N < 10^9












class Solution {
public:
    int bitwiseComplement(int N) {
        if(N==0) return 1;
        int bits = floor(log2(N))+1;
        long long tmp = (long long)(1 << bits) - 1;
        return N ^ tmp;
    }
};




// num + comlement = all onesa

class Solution {
public:
    int bitwiseComplement(int n) {
        if(n==0) return 1;
        int digits=log2(n)+1;
        return pow(2, digits)-1-n;
    }
};





class Solution {
public:
    int bitwiseComplement(int n) {
        if(n==0) return 1;
        string binary;
        while(n){
            binary+=to_string(n%2);
            n/=2;
        }
        int len=binary.length();

        for(int i=0;i<len;i++){
            if(binary[i]=='0') binary[i]='1';
            else binary[i]='0';
        }

        int res=0;

        for(int i=0;i<len;i++){
            res+=pow(2, i)*(binary[i]-'0');
        }

        return res;
    }
};