DouKaku?

#include <iostream>
#include <string>

std::string remove_comment(const std::string& s)
{
    std::string ret;

    std::string::size_type i1 = 0;

    while (1)
    {
        std::string::size_type i2;

        if ((i2 = s.find("/*", i1)) == std::string::npos)
        {
            ret.append(s.substr(i1));

            break;
        }
        else
        {
            ret.append(s.substr(i1, i2 - i1));

            i1 = i2 + 2;
        }

        if ((i2 = s.find("*/", i1)) == std::string::npos)
        {
            break;
        }
        else
        {
            i1 = i2 + 2;
        }
    }

    return ret;
}

void run(const std::string& s)
{
    std::cout << remove_comment(s) << std::endl;
}

int main()
{
    run("AAA");
    run("AAA/*BBB*/");
    run("AAA/*BBB");
    run("AAA/*BBB*/CCC");
    run("AAA/*BBB/*CCC*/DDD*/EEE");
    run("AAA/a//*BB*B**/CCC");
}