C++/STL Algorithms Binary search/upper bound

lower_bound and upper_bound

<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 <vector>
3. include <deque>
4. include <list>
5. include <set>
6. include <map>
7. include <string>
8. include <algorithm>
9. include <iterator>
10. include <functional>
11. include <numeric>

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;

} /* INSERT_ELEMENTS (collection, first, last)

* - fill values from first to last into the collection
* - NOTE: NO half-open range
*/

template <class T> inline void INSERT_ELEMENTS (T& coll, int first, int last) {

   for (int i=first; i<=last; ++i) {
       coll.insert(coll.end(),i);
   }

}

int main() {

   list<int> coll;
   INSERT_ELEMENTS(coll,1,9);
   INSERT_ELEMENTS(coll,1,9);
   coll.sort ();
   PRINT_ELEMENTS(coll);
   // print first and last position 5 could get inserted
   list<int>::iterator pos1, pos2;
   pos1 = lower_bound (coll.begin(), coll.end(), 5);
   pos2 = upper_bound (coll.begin(), coll.end(), 5);
   cout << "5 could get position " << distance(coll.begin(),pos1) + 1
        << " up to "               << distance(coll.begin(),pos2) + 1
        << " without breaking the sorting" << endl;
   // insert 3 at the first possible position without breaking the sorting
   coll.insert (lower_bound(coll.begin(),coll.end(),
                            3),
                3);
   // insert 7 at the last possible position without breaking the sorting
   coll.insert (upper_bound(coll.begin(),coll.end(),
                            7),
                7);
   PRINT_ELEMENTS(coll);

} /* 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 5 could get position 9 up to 11 without breaking the sorting 1 1 2 2 3 3 3 4 4 5 5 6 6 7 7 7 8 8 9 9

*/        
 </source>

Return iterator from std::upper_bound

<source lang="cpp">

1. include <iostream>

using std::cout; using std::endl;

1. include <algorithm>
2. include <vector>
3. include <iterator>

int main() {

  int a1[ 10 ] = { 2, 2, 4, 4, 4, 6, 6, 6, 6, 8 };
  std::vector< int > v( a1, a1 + 10 );
  std::ostream_iterator< int > output( cout, " " );
  std::copy( v.begin(), v.end(), output );
  // determine upper-bound insertion point for 6 in v
  std::vector< int >::iterator upper;
  upper = std::upper_bound( v.begin(), v.end(), 6 );
  cout << "::"<< ( upper - v.begin() );
  return 0;

} /* 2 2 4 4 4 6 6 6 6 8 ::9

*/        
 </source>