reading info form a vector pair and array

[kmce]

I have an vector declared as vector<pair<pair<int, int>, int> >adj[];

is it possible to iterate through the vector and search for a value stored in the first int, and return a value stored in the second int, if the first int is found. There are multiple of the same values stored in the first int.


vector declaration

   vector<pair<pair<int, int>, int> >adj[];

[Ganado]

Just to be clear: What you currently have isn't just a vector<...>, it's an array of vector<...>, with a size you have not specified.
Is that intended?

When you say "search for a value stored in the first int", are you referring to the int in the outer pair, or the first int in the inner pair?
PS: It would probably be more readable if you turned this into vector of some sort of named struct, in my opinion.
What is this construct supposed to actually represent?

[kmce]

i was told not to declare it, I did have it declared and was told it was wrong?

the int in the first pair. the very first one that is declared

[Ganado]

I don't know what your instructor said or meant, but I would imagine they meant you should remove the "[]" from the declaration.

// Example program
#include <iostream>
#include <string>
#include <vector>
#include <utility>

using namespace std;

using my_pair = pair< pair<int, int>, int >; // for my sanity

int search(const vector<my_pair>& vec, int search_value)
{
    // iterate through vector
    for (const auto& element : vec)
    {
        // Search for a value stored in the first int (of the inner pair)
        int value = element.first.first;

        // if the first int is found
        if (search_value == value)
        {
            // return a value stored in the second int
            return element.first.second;   
        }
    }
    
    // TODO: What happens if element is not found?
    std::cout << "ERROR: Element not found!\n";
    return -1;
}

int main()
{
    vector<my_pair> adj;
    
    adj.push_back( my_pair { {41, 42}, 43} );
    adj.push_back( my_pair { {104, 105}, 106} );
    
    int resultA = search(adj, 41);
    std::cout << "resultA = " << resultA << '\n';
    
    int resultB = search(adj, 104);
    std::cout << "resultB = " << resultB << '\n';
}

resultA = 42
resultB = 105

Note that I never used the pair.second.second, since I don't know what you want to do with it.

[kmce]

I more than likely never explained myself well enough with the whole vector array declaration and thats why i was told to remove it. Thank you for the code, I will try that

[kmce]

The code did work, but i do need it to be an array of vectors, how would I edit it to work with that?

[deleted account xyzzy]

To properly use a C-style array you have to declare its size before use. Either on the stack or on the heap with new[]. You declared an array on the stack with ZERO elements, and it can't be resized during run-time without a lot of work-arounds.

Either you are misunderstanding the requirements of the assignment, or the person who created the assignment is a sadist. A C-style array with a type of std::vector with a type of nested std::pairs is not something a sane person would require.

A C-style array of std::vector appears (to me) to attempt to create a 2 dimensional container, very badly.

Maybe posting what the assignment requirements are so we can better decipher what needs to be done to go forward.

[Ganado]

If we go back to your original declaration,you could do something like:

    vector<my_pair> adj[] = {
        vector<my_pair> { my_pair { {41, 42}, 43},
                          my_pair { {100, 101}, 102} },
                          
        vector<my_pair> { my_pair { {51, 52}, 53},
                          my_pair { {200, 300}, 222} },
                          my_pair { {300, 300}, 322} }           
    };
    
    search(adj, 2, 41);

The "search" function I made would be changed to have a outline like:

int search(const vector<my_pair> arr[], int num_elements, int search_value)
{
    // return (...);
}

And now you just need to loop num_elements times over arr, and then within each loop of that, loop over each vector.