Returns an iterator to the first element in a map with a key value that is equal to or greater than that of a specified key.
iterator lower_bound(
const Key& _Key
);
const_iterator lower_bound(
const Key& _Key
) const;
Parameters
- _Key
The argument key value to be compared with the sort key of an element from the map being searched.
Return Value
An iterator or const_iterator that addresses the ___location of an element in a map that with a key that is equal to or greater than the argument key, or that addresses the ___location succeeding the last element in the map if no match is found for the key.
If the return value of lower_bound is assigned to a const_iterator, the map object cannot be modified. If the return value of lower_bound is assigned to an iterator, the map object can be modified.
Example
// map_lower_bound.cpp
// compile with: /EHsc
#include <map>
#include <iostream>
int main( )
{
using namespace std;
map <int, int> m1;
map <int, int> :: const_iterator m1_AcIter, m1_RcIter;
typedef pair <int, int> Int_Pair;
m1.insert ( Int_Pair ( 1, 10 ) );
m1.insert ( Int_Pair ( 2, 20 ) );
m1.insert ( Int_Pair ( 3, 30 ) );
m1_RcIter = m1.lower_bound( 2 );
cout << "The first element of map m1 with a key of 2 is: "
<< m1_RcIter -> second << "." << endl;
// If no match is found for this key, end( ) is returned
m1_RcIter = m1. lower_bound ( 4 );
if ( m1_RcIter == m1.end( ) )
cout << "The map m1 doesn't have an element "
<< "with a key of 4." << endl;
else
cout << "The element of map m1 with a key of 4 is: "
<< m1_RcIter -> second << "." << endl;
// The element at a specific ___location in the map can be found
// using a dereferenced iterator addressing the ___location
m1_AcIter = m1.end( );
m1_AcIter--;
m1_RcIter = m1. lower_bound ( m1_AcIter -> first );
cout << "The element of m1 with a key matching "
<< "that of the last element is: "
<< m1_RcIter -> second << "." << endl;
}
The first element of map m1 with a key of 2 is: 20. The map m1 doesn't have an element with a key of 4. The element of m1 with a key matching that of the last element is: 30.
Requirements
Header: <map>
Namespace: std