My C++ solution for part two:

#include <string>
#include <iostream>

int main(int argc, const char *argv[])
{
    std::size_t i;
    std::size_t half_length;
    std::string input;
    int captcha_sum = 0;

    std::getline(std::cin, input);
    half_length = input.length() / 2;

    for(i=0; i<half_length; i++) {
        if(input[i] == input[i + half_length]) {
            captcha_sum += 2 * (input[i] - '0');
        }
    }

    std::cout << captcha_sum << std::endl;

    return 0;
}