C++/STL Algorithms Binary search/upper bound
lower_bound and upper_bound
/* 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.
*/
#include <iostream>
#include <vector>
#include <deque>
#include <list>
#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <functional>
#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
*/
Return iterator from std::upper_bound
#include <iostream>
using std::cout;
using std::endl;
#include <algorithm>
#include <vector>
#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
*/