C++ Tutorial/set multiset/set compare

Compare sets with "==" operator

<source lang="cpp">#include <set>

1. include <iostream>
2. include <string>

using namespace std; template <class T> void print(T& c){

  for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
     std::cout << *i << endl;
  }

} int main() {

 set<string> first;
 first.insert("r");
 first.insert("T");
 first.insert("s");
 cout << first.size() << endl;
 set<string> second (first);   // Copy constructor
 second.insert("r");
 second.insert("K");
 second.insert("S");
 second.insert("b");
 cout << second.size() << endl;
 // Are the sets the same?
 if (first == second)
   cout << "Sets have same elements\n";
 else
   cout << "Not same elements\n";

}</source>

set comparison

<source lang="cpp">/* The following code example is taken from the book

* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/

1. include <iostream>
2. include <set>

using namespace std; /* PRINT_ELEMENTS()

* - prints optional C-string optcstr followed by
* - all elements of the collection coll
* - separated by spaces
*/

template <class T> inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="") {

   typename T::const_iterator pos;
   std::cout << optcstr;
   for (pos=coll.begin(); pos!=coll.end(); ++pos) {
       std::cout << *pos << " ";
   }
   std::cout << std::endl;

}

// type for sorting criterion template <class T> class RuntimeCmp {

 public:
   enum cmp_mode {normal, reverse};
 private:
   cmp_mode mode;
 public:
   // constructor for sorting criterion
   // - default criterion uses value normal
   RuntimeCmp (cmp_mode m=normal) : mode(m) {
   }
   // comparison of elements
   bool operator() (const T& t1, const T& t2) const {
       return mode == normal ? t1 < t2 : t2 < t1;
   }
   // comparison of sorting criteria
   bool operator== (const RuntimeCmp& rc) {
       return mode == rc.mode;
   }

}; // type of a set that uses this sorting criterion typedef set<int,RuntimeCmp<int> > IntSet; // forward declaration void fill (IntSet& set); int main() {

   // create, fill, and print set with normal element order
   // - uses default sorting criterion
   IntSet coll1;
   fill(coll1);
   PRINT_ELEMENTS (coll1, "coll1: ");
   // create sorting criterion with reverse element order
   RuntimeCmp<int> reverse_order(RuntimeCmp<int>::reverse);
   // create, fill, and print set with reverse element order
   IntSet coll2(reverse_order);
   fill(coll2);
   PRINT_ELEMENTS (coll2, "coll2: ");
   // assign elements AND sorting criterion
   coll1 = coll2;
   coll1.insert(3);
   PRINT_ELEMENTS (coll1, "coll1: ");
   // just to make sure...
   if (coll1.value_comp() == coll2.value_comp()) {
       cout << "coll1 and coll2 have same sorting criterion"
            << endl;
   }
   else {
       cout << "coll1 and coll2 have different sorting criterion"
            << endl;
   }

} void fill (IntSet& set) {

   // fill insert elements in random order
   set.insert(4);
   set.insert(7);
   set.insert(5);
   set.insert(1);
   set.insert(6);
   set.insert(2);
   set.insert(5);

}</source>

coll1: 1 2 4 5 6 7
coll2: 7 6 5 4 2 1
coll1: 7 6 5 4 3 2 1
coll1 and coll2 have same sorting criterion