gistfile1.cpp

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

using namespace std;

void merge(vector<string>& v)
{
   bool any;

   do
   {
      size_t i = 0;
      any = false;

      while (i < v.size())
      {
         size_t j = i + 1;

         while (j < v.size())
         {
            if (v[i].find_first_of(v[j]) != string::npos)
            {
               sort(v[i].begin(), v[i].end());
               sort(v[j].begin(), v[j].end());
               string tmp;
               set_union(v[i].begin(), v[i].end(),
                         v[j].begin(), v[j].end(),
                         std::back_inserter(tmp));
               v[i] = tmp;
               v.erase(v.begin() + j);
               any = true;
            }
            else
            {
               ++j;
            }
         }

         ++i;
      }
   }
   while (any);
}

int main()
{
   vector<string> v;
   v.push_back("abc");
   v.push_back("def");
   v.push_back("cf");
   v.push_back("ghi");
   v.push_back("jkl");
   v.push_back("mno");
   v.push_back("pqtl");

   merge(v);

   for (const std::string& s : v)
   {
      cout << s << endl;
   }
}