string validation in std::vector

I am working on a code where I need to validate a std::vector filled with multiple std::string objects. The logic is that I need to check if all of the objects are valid or not. If yes then display a message saying that input vector is valid, error otherwise. Here is what I have so far.

#include<iostream>
#include<vector>
#include<numeric>
#include<boost/foreach.hpp>

short multiply(short s1,short s2)
{
    return s1*s2;
}
bool validate(const std::vector<std::string> &in)
{
    std::vector<short>check(in.size(),0);
    auto checkitr = check.begin();

    BOOST_FOREACH(std::string str,in)
    {
        for(auto itr = str.begin(); itr != str.end(); ++itr)
        {
            if(*itr == 'c')
            {
                *checkitr = 1;
                break;
            }
        }
        ++checkitr;
    }
    short product = std::accumulate(check.begin(),check.end(),1,multiply);

    return ( (product) ? true : false );
}

int main()
{
    std::string s1("abcd");
    std::string s2("lncd");
    std::vector<std::string>iVec;

    iVec.push_back(s1);
    iVec.push_back(s2);

    bool isValid = validate(iVec);

    if(isValid){
        std::cout<<"This Vector is valid   "<<std::endl;    
    }
    else
    {   
        std::cout<<"This is an invalid vector  "<<std::endl;        
    }

    iVec.push_back(std::string("ghkd"));

    isValid = validate(iVec);

    if(isValid){
        std::cout<<"This Vector is valid  "<<std::endl;

    }
    else
    {
        std::cout<<"This is an invalid vector  "<<std::endl;
    }   

    return 0;
}

This runs fine and gives me the result that I need.My question is, Is there any other better/performance efficient approach in standard algorithm or boost library that I can use instead of my current approach?