CODEWITHSUNDEEP
c++vector2d
user977154
user977154

Reputation: 1095

Iterate through a vector column C++

I am wanting to iterate through my entire column that contains the type double and divide each value by the size of the column. This will give me the frequency. I would have not issue doing this in an array or any other datatype. I am still learning about the vectors. Here is the 2D vector type that I am trying to manipulate 

vector<pair<char, double>> output;

Upvotes: 0

Views: 1730

Answers (3)

4pie0
4pie0

Reputation: 29724

std::pair is a struct template that provides a way to store two heterogeneous objects as a single unit.

if you have a vector of pairs this means you will access data through pair interface . You can get first data of pair via first member and second via second.

for(std::vector<std::pair <char, double> >::const_iterator vpci = arg.begin(); 
    vpci != arg.end(); ++vpci) {
        cout << vpci->first << "->" << vpci->second;
}

or even better, maybe create a template:

template <typename T1, typename T2>
void prn_vecOfPair(const std::vector<std::pair <T1, T2> > &arg, string sep ="") {
    for(std::vector<std::pair <T1, T2> >::const_iterator vpci = arg.begin(); 
        vpci != arg.end(); ++vpci) {
        cout << vpci->first << "->" << vpci->second << sep;
    }
}

in C++11 this (as usual) can be done much easier:

for (auto & i : output)
{
   cout << i->first << "->" << i->second << "\n";
}

Upvotes: 1

billz
billz

Reputation: 45410

If you have C++11:

for (auto & p : output)
{
   cout << p.first << " " << p.second << "\n";
}
std::cout << std::endl;

or with C++03

for (std::vector<std::pair<char, double> >::iterator it = output.begin(); 
     it != output.end(); ++it)
{
   cout << it .first << " " << it .second << "\n";
}
std::cout << std::endl;

Upvotes: 2

Jonathan Potter
Jonathan Potter

Reputation: 37132

You can treat a vector just like an array, and access the elements using []. For example:

for (size_t i = 0; i < output.size(); ++i)
{
    pair<char, double>& element = output[i]; // access element i in the vector
    cout << element.first; // prints the first member of the pair
    cout << element.second; // prints the second member of the pair
}

Upvotes: 1

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