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Power Set

duude1234 (3)
Hi,

I need to calculate the power set of a set of a given numbers (not for a homework assignment). I found a piece of code online:

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#include <iostream>
#include <set>
#include <vector>
#include <iterator>
#include <algorithm>
typedef std::set<int> set_type;
typedef std::set<set_type> powerset_type;
 
powerset_type powerset(set_type const& set)
{
  typedef set_type::const_iterator set_iter;
  typedef std::vector<set_iter> vec;
  typedef vec::iterator vec_iter;
 
  struct local
  {
    static int dereference(set_iter v) { return *v; }
  };
 
  powerset_type result;
 
  vec elements;
  do
  {
    set_type tmp;
    transform(elements.begin(), elements.end(),
                   std::inserter(tmp, tmp.end()),
                   local::dereference);
    result.insert(tmp);
    if (!elements.empty() && ++elements.back() == set.end())
    {
      elements.pop_back();
    }
    else
    {
      set_iter iter;
      if (elements.empty())
      {
        iter = set.begin();
      }
      else
      {
        iter = elements.back();
        ++iter;
      }
      for (; iter != set.end(); ++iter)
      {
        elements.push_back(iter);
      }
    }
  } while (!elements.empty());
 
  return result;
}
 
int main()
{
  int values[4] = { 2, 3, 5, 7 };
  set_type test_set(values, values+4);
 
  powerset_type test_powerset = powerset(test_set);
 
  for (powerset_type::iterator iter = test_powerset.begin();
       iter != test_powerset.end();
       ++iter)
  {
    std::cout << "{ ";
    char const* prefix = "";
    for (set_type::iterator iter2 = iter->begin();
         iter2 != iter->end();
         ++iter2)
    {
      std::cout << prefix << *iter2;
      prefix = ", ";
    }
    std::cout << " }\n";
  }
}


However, when I try to compile this, it tells me:
In function `powerset(std::set<int, std::less<int>, std::allocator<int> > const&)':
/usr/include/c++/4.5/bits/stl_tree.h:1224: multiple definition of `powerset(std::set<int, std::less<int>, std::allocator<int> > const&)'

dangrr888 (80)
Hi duude1234,

compiles fine on my mac (gcc 4.2.1)


./power 
{  }
{ 2 }
{ 2, 3 }
{ 2, 3, 5 }
{ 2, 3, 5, 7 }
{ 2, 3, 7 }
{ 2, 5 }
{ 2, 5, 7 }
{ 2, 7 }
{ 3 }
{ 3, 5 }
{ 3, 5, 7 }
{ 3, 7 }
{ 5 }
{ 5, 7 }
{ 7 }
Jimbot (29)

Also complies fine for me using g++ 4.5.2 on Ubuntu Linux

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