CODEWITHSUNDEEP
c++vector
user2374907
user2374907

Reputation: 55

C++ number of unique elements

Hi I have this function that gets the unique elements from a vector, but I was wondering how can make it get me the number of those unique elements as well.

void getUniqueSellers(vector<string> & result) {
        vector<CService>::iterator i= m_vData.begin();

        while(i != m_vData.end()) {

            if(find(result.begin(), result.end(), (*i).GetSeller()) == result.end()) {
                result.push_back((*i).GetSeller());
            }

            i++;
        }
    }

void main() 
{
    vector<string> res;
    myAnalyzer.getUniqueSellers(res);
    vector<string>::iterator i=res.begin();
    while(i!=res.end()) {
        cout<< *i<<",";
        i++;
    }
    system("pause");
    return;
}

Upvotes: 1

Views: 1427

Answers (2)

Qaz
Qaz

Reputation: 61900

Since you already have a list of them, it's easy to find the size:

res.size()

However, I suggest you drop the recreated algorithm to do it and use an existing one. I also suggest you return a value instead of using an out parameter:

std::vector<std::string> getUniqueSellers() {
    std::sort(m_vData.begin(), m_vData.end());
    m_vData.erase(std::unique(m_vData.begin(), m_vData.end()), m_vData.end());

    std::vector<std::string> res;
    std::transform(m_vData.begin(), m_vData.end(), std::back_inserter(res), [](const CService &cs) {return cs.GetSeller();});

    return res;
}

I used a C++11 lambda, so you can replace that with a normal functor if you don't have C++11. This also requires you to implement equality for CService based on GetSeller(). Alternatively, if you don't want to modify m_vData, you can make a copy or use std::set:

std::set<std::string> res;
std::transform(m_vData.begin(), m_vData.end(), std::back_inserter(res), [](const CService &cs) {return cs.GetSeller();});
return std::vector(res.begin(), res.end());

Upvotes: 3

Sam I am says Reinstate Monica
Sam I am says Reinstate Monica

Reputation: 31184

Instead of returning a vector of string, you can make a class of seller that contains a string name and an int count. and return a vector of that.

If you find a duplicate, instead of ignoring it, you can just incriment the count

Upvotes: 0

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