How to sort string in class using stl vector

Question

I want to sort a name list using std::sort. The problem is that I can only sort first name instead of firstname and last name together, the class I have create is like this:

class Name{
public:
Name(string first, string last):firstName(first), lastName(last){};

string getFirstName() const{
    return firstName;
};

string getLastName() const{
    return lastName;
}

private:
string firstName;
string lastName;
};

Once I get first name and last name I store them in the class Name, but I read them from a file, and the code is like this

file.open("namelist.txt");

vector<string> strvec;
while (!file.eof()){
    string firstName, lastName;
    file >> firstName;
    file >> lastName;
    Name n(firstName,lastName);
    strvec.push_back(firstName);

}

As you can see I store first Name in the vector, so I can sort using

sort(strvec.begin(),strvec.end());

But I only sort the first name instead of all together, the idea of using class is that i could sort them together, my idea is using vector<Name> strvec but I don't know how to add firstname and lastname together in the vector, does anyone have idea of doing it?

score 1 · Accepted Answer · answered Dec 12 '13 at 23:21

std::sort provides ways of plugging in your own ordering functions.

You need to provide either a functor to the sort function, or a less than operator for your name class:

struct Name_Compare {
    bool operator()(const Name& a, const Name& b) {
        return a.getFirstName() < b.getFirstName();
    }
}

std::sort(names.begin(), names.end(), Name_Compare());

OR:

bool operator<(const Name& a, const Name& b) {
    return a.getFirstName() < b.getFirstName();
}

std::sort(names.begin(), names.end());

Or, if you're compiling with C++11, you can do this all inline with a lambda:

std::vector<Name> names;

//Add your names...

std::sort(names.begin(), names.end(), 
          [](const Name& a, const Name& b) { 
              return a.getFirstName() < b.getFirstName()
          });

The functor or lambda is probably your best choice here. Making an operator< for this class says that you always want to sort by first name, which is probably not true in general for names.

How to sort string in class using stl vector

1 Answers1