Retrieve the value stored in a multiset

Question

I am trying to retrieve the value that is stored in a particular spot in a mulitset, but all I'm unable to find out how to do that anywhere online. This is also my first time using multisets in C++.

The multiset that I want to get the value from is the numerator, and it's declared in the header file that I attached to my program. Below is what I have tried.

// This method will swap the numerator and denominator values
void Fraction::Invert() {
    int tmp = 0;

    for (int i = 0; i < (int)numerator.size(); i++) {
        // I want the value stored in the multiset (numerator) at i
        tmp = numerator.find(i);
    }
}

Answer 1

Many methods exist so you can retrieve a value from a multiset.

First:

You can use an iterator. Something like below:

    for (auto cit = numerator.cbegin(); cit != numerator.cend(); cit++)
        std::cout << *cit << std::endl;

In the your example, it is like below:

// This method will swap the numerator and denominator values
void Fraction::Invert() {
    int tmp = 0;

    auto cit = numerator.cbegin();
    for (int i = 0; i < (int)numerator.size() && cit != numerator.cend(); i++, cit++) {
        // I want the value stored in the multiset (numerator) at i
        tmp = *cit; // *cit is the value of i'th number of multiset
    }
}

Second:

You can use the range for style:

    for (auto value : numerator)
        std::cout << value << std::endl;

And in the your example, it is like below:

// This method will swap the numerator and denominator values
void Fraction::Invert() {
    int tmp = 0;

    int i = 0;
    for (auto value : numerator) {
        // I want the value stored in the multiset (numerator) at i
        tmp = value; // value is the value of i'th number of multiset
        ++i;
    }
}