#include <iostream>
#include <string>
#include <boost/regex.hpp>

std::string foo(const std::string &input) {
    // R"(...)" - c++11'ный аналог шарповского @"..."
    boost::regex r(R"(\([^()]+\)|(([a-z]|\*)+))");
    return boost::regex_replace(input, r, [] (const boost::smatch &s) -> std::string {
        return std::string(s.length(), ' ');
    });
}

void test(const std::string &in, const std::string &expected_out) {
    std::string real_out = foo(in);
    if (real_out == expected_out) {
        std::cout << "PASS" << std::endl;
    } else {
        std::cout << "FAIL: got \"" << real_out << "\" instead of \"" <<
            expected_out << "\"" << std::endl;
    }
}

int main() {
    test("", "");
    test("a", " ");
    test("a*b*c", "     ");
    test("a+b", " + ");
    test("(a+b*c)+x*y", "       +   ");
    test("(a+b*c)+x+y", "       + + ");
    test("(a+b*c)+x+y+", "       + + +");
    return 0;
}