C++ STL set, lower_bound() program example

Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Header file: Standard

Additional library: none/default

Additional project setting: Set project to be compiled as C++

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C++ Code (/TP)

Other info: none

To do: Using the C++ lower_bound() to return an iterator to the first element in a set with a key that is equal to or greater than a specified key in C++ programming

To show: How to use the C++ set, lower_bound() to return an iterator to the first element in a set with a key that is equal to or greater than a specified key in C++ programming

// C++ STL set, lower_bound()

#include <set>

#include <iostream>

using namespace std;

int main(void)

{

// container

set <int> st1;

// iterators

set <int> :: const_iterator st1Iter, st1_PIter, st1_QIter;

// push/insert data

st1.insert(11);

st1.insert(21);

st1.insert(30);

st1.insert(10);

st1.insert(22);

// print the data and do other operations

cout<<"st1 set data: ";

for(st1Iter = st1.begin(); st1Iter != st1.end(); st1Iter++)

cout<<" "<<*st1Iter;

cout<<endl;

st1_QIter = st1.lower_bound(21);

cout<<"The element of st1 set with a key of 21 is: "<<*st1_QIter<<endl;

st1_QIter = st1.lower_bound(60);

// if no match is found for the key, end() is returned

if(st1_QIter == st1.end())

cout<<"The st1 set doesn't have an element with a key of 60"<<endl;

else

cout<<"The element of set st1 with a key of 60 is: "<<*st1_QIter<<endl;

// the element at a specific location in the set can be found by using a dereferenced iterator that addresses the location

st1_PIter = st1.end();

st1_PIter--;

st1_QIter = st1.lower_bound(*st1_PIter);

cout<<"The element of st1 with a key matching that of the last element is: "<<*st1_QIter<<endl;

return 0;

}

Output examples:

st1 set data: 10 11 21 22 30

The element of st1 set with a key of 21 is: 21

The st1 set doesn't have an element with a key of 60

The element of st1 with a key matching that of the last element is: 30

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