The sample code below illustrates how to use the set::lower_bound, set::upper_bound, and set::equal_range STL functions in Visual C++.
Required Header:
<set>
template<class _K, class _Pr, class _A>
class set
{
public:
// Function 1:
const_iterator lower_bound(const _K& _Kv) const;
// Function 2:
const_iterator upper_bound(const _K& _Kv) const;
// Function 3:
_Paircc equal_range(const _K& _Kv) const;
}
Note: The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.
Description:
The lower_bound function returns an iterator to the earliest element in the controlled sequence that has a key that does not match the value passed to the lower_bound function. The upper_bound function returns an iterator to the earliest element in the controlled sequence that has a key matching the value passed to the upper_bound function. If no such element exists, the function returns end(). In both cases, the function set::key_comp()(key, x) is used to determine if the keys match. The equal_range function returns a pair value, where .first is the result of the lower_bound function, and .second is the result of the upper_bound function.
Sample Code:
//////////////////////////////////////////////////////////////////////
//
// Compile options needed: -GX
//
// SetBoundRange.cpp:
// Illustrates how to use the lower_bound function to get an
// iterator to the earliest element in the controlled sequence
// that has a key that does not match the value passed to the
// function. It also illustrates how to use the upper_bound
// function to get an iterator to the earliest element in the
// controlled sequence that has a key that matches the value
// passed to the function. The last thing it illustrates is
// how to use the equal_range function to get a pair value that
// contains the lower_bound and upper_bound results of the key.
//
// Functions:
//
// lower_bound Returns an iterator whose value does not match the
// key passed to the function, or end() if no such
// element exists.
// upper_bound Returns an iterator whose value matches the key
// passed to the function, or end() if no such element
// exists.
// equal_range Returns a pair of (lower_bound,upper_bound).
//////////////////////////////////////////////////////////////////////
#pragma warning(disable:4786)
#include <set>
#include <iostream>
using namespace std ;
typedef set<int> SET_INT;
void main() {
SET_INT s1;
SET_INT::iterator i;
cout << "s1.insert(5)" << endl;
s1.insert(5);
cout << "s1.insert(10)" << endl;
s1.insert(10);
cout << "s1.insert(15)" << endl;
s1.insert(15);
cout << "s1.insert(20)" << endl;
s1.insert(20);
cout << "s1.insert(25)" << endl;
s1.insert(25);
cout << "s1 -- starting at s1.lower_bound(12)" << endl;
// prints: 15,20,25
for (i=s1.lower_bound(12);i!=s1.end();i++)
cout << "s1 has " << *i << " in its set." << endl;
cout << "s1 -- starting at s1.lower_bound(15)" << endl;
// prints: 15,20,25
for (i=s1.lower_bound(15);i!=s1.end();i++)
cout << "s1 has " << *i << " in its set." << endl;
cout << "s1 -- starting at s1.upper_bound(12)" << endl;
// prints: 15,20,25
for (i=s1.upper_bound(12);i!=s1.end();i++)
cout << "s1 has " << *i << " in its set." << endl;
cout << "s1 -- starting at s1.upper_bound(15)" << endl;
// prints: 20,25
for (i=s1.upper_bound(15);i!=s1.end();i++)
cout << "s1 has " << *i << " in its set." << endl;
cout << "s1 -- s1.equal_range(12)" << endl;
// does not print anything
for (i=s1.equal_range(12).first;i!=s1.equal_range(12).second;i++)
cout << "s1 has " << *i << " in its set." << endl;
cout << "s1 -- s1.equal_range(15)" << endl;
// prints: 15
for (i=s1.equal_range(15).first;i!=s1.equal_range(15).second;i++)
cout << "s1 has " << *i << " in its set." << endl;
}
Program Output is:
s1.insert(5)
s1.insert(10)
s1.insert(15)
s1.insert(20)
s1.insert(25)
s1 -- starting at s1.low
s1 has 15 in its set.
s1 has 20 in its set.
s1 has 25 in its set.
s1 -- starting at s1.low
s1 has 15 in its set.
s1 has 20 in its set.
s1 has 25 in its set.
s1 -- starting at s1.upp
s1 has 15 in its set.
s1 has 20 in its set.
s1 has 25 in its set.
s1 -- starting at s1.upp
s1 has 20 in its set.
s1 has 25 in its set.
s1 -- s1.equal_range(12)
s1 -- s1.equal_range(15)
s1 has 15 in its set.