all combination question

[codeback99]

Hello all

for example let say there is vector [1,2,3,4,5,6,7,8,9]
and let say there is int n

if i say n=3
I want to find all possible 3 combination
[1,2,3][1,2,4].....such and such

if i say n=4
[1,2,3,4][1,2,3,5]......

I want to know how you write the code depend on the input n
is it call dynamic programming?

[IceThatJaw]

It's not a programming problem. It's a discrete Math problem. Solve that, and the program will write itself.

[codeback99]

U don't understand the question dude

[Duthomhas]

Er, not these days, no.

A simple solution using the STL

#include <algorithm>
#include <iostream>
#include <iterator>
#include <vector>
using namespace std;

size_t factorial( size_t n )
  {
  size_t result = 1;
  while (n > 1)
    result *= n--;
  return result;
  }

template <typename Iterator>
bool next_take_r( size_t r, Iterator begin, Iterator end )
  {
  bool result = false;
  size_t n = factorial( distance( begin, end ) - r );
  for (size_t x = 0; x < n; x++)
    result = next_permutation( begin, end );
  return result;
  }

int main()
  {
  vector <int> ns { 1, 2, 3, 4, 5, 6, 7, 8, 9 };

  size_t n = 3;
  
  do {
    copy_n( ns.begin(), min( n, ns.size() ), ostream_iterator <int> ( cout, " " ) );
    cout << "\n";
    }
  while (next_take_r( n, ns.begin(), ns.end() ));

  return 0;
  }

Compile with C++11 support.

Enjoy!

[codeback99]

Thanks

is visual studio 2012 support c++11?