make_tuple() from vector elements & storing varied tuple_size<T> tuples

**sean_cantab** · 11-08-2016

Larger number: N, smaller number: K
Task:

Code:

for (k = 1; k <= K; k++)

to choose k from N and save the results of all such possible combinations for each k in suitable container(s) that can be acccessed (directly or through pointers)

What I have so far: code (thanks Google) to generate each of these combinations for 1 through K and, I think, a way of capturing each particular combination for each k in a vector
Outstandings, etc: (a) how to do a make_tuple() with the elements of this vector directly (assuming tuple is the best container to save each particular result?) (b) how do I store and access these tuples (via pointers?) as the type of the tuple changes with k or do I need K containers (c) or maybe there is some other way of approaching this problem that I have overlooked?

Code that will work and output to console: #10958326 - Pastie

Code that will not produce any visible output because it has been edited and commented to show outstandings (a) and (b) from above:

Code:

#include <iostream>
#include <algorithm>
#include <string>
#include<vector>
#include<ctime>

using namespace std;

int main()
{
    cout<<"Choose N: ";
    int N;
    cin>> N;
    cout<<"Choose K: ";
    int K;
    cin>>K;


    clock_t tStart = clock();
    for (int j = 1; j <= K; j++)
    {
        string bitmask(j, 1);
        bitmask.resize(N, 0);


        do
        {
            vector<int> v{};
            for (int i = 0; i < N; ++i)
            {
                if (bitmask[i]) v.emplace_back(i+1);
            }
            //make_tuple(v.begin(),v.end()) // doesn't work;
            //place tuple_size<j> in a container;
            //    cout << "\n";
        }   while (prev_permutation(bitmask.begin(), bitmask.end()));
            //tuple_size<j> increases by 1 from next j loop ;
    }
    cout<<"Time taken: "<<(clock() - tStart)/CLOCKS_PER_SEC<<" secs\n";
}

Thanks, as always, for any help, suggestions

**algorism** · 11-08-2016

Code:

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <chrono>
using namespace std;

int main() {
    int N, K;
    cout << "Choose N: ";
    cin >> N;
    cout << "Choose K: ";
    cin >> K;

    vector<vector<int>*> w;

    auto tStart = chrono::high_resolution_clock::now();

    for (int i = 1; i <= K; i++) {
        string bits(i, 1);
        bits.resize(N, 0);
        do {
            w.push_back(new vector<int>());
            for (int j = 0; j < N; ++j)
                if (bits[j])
                    w[w.size()-1]->push_back(j + 1);
        } while (prev_permutation(bits.begin(), bits.end()));
    }

    auto tEnd = chrono::high_resolution_clock::now();

    for (const auto& combo: w) {
        for (int num: *combo)
            cout << num << ' ';
        cout << '\n';
    }

    cout << chrono::duration_cast<chrono::milliseconds>
            (tEnd - tStart).count() << " ms\n";

    for (auto& combo: w)
        delete combo;
}

**sean_cantab** · 11-08-2016

Wow! and not a tuple in sight! Many thanks

I also managed to figure out make_tuple with vector elements directly and then access the elements of the tuple:

Code:

#include <iostream>
#include<vector>
#include<tuple>

using namespace std;

int main()
{
    vector<int> v {1, 2, 3, 4};
    auto myTuple = make_tuple(v.begin(), v.end());
    for (size_t i = 0; i < v.size(); i++)
    {
        cout<<*(get<0>(myTuple)+i)<<"\t";
    }
}

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