Predicate Version of lower_bound
Illustrates how to use the predicate version of the lower_bound Standard Template Library (STL) function in Visual C++.
template<class ForwardIterator, class T, class Compare>
inline ForwardIterator lower_bound(
ForwardIterator First,
ForwardIterator Last,
const T& Value,
Compare Compare
)
Remarks
备注
The class/parameter names in the prototype do not match the version in the header file. Some have been modified to improve readability.
The lower_bound algorithm returns the first location in the sequence that value can be inserted such that the order of the sequence is maintained. lower_bound returns an iterator positioned at the location that value can be inserted in the range [First..Last), or returns Last if no such position exists. This version assumes the range [First..Last) is sorted sequentially using the compare function.
Example
// lower_boundPV.cpp
// compile with: /EHsc
// Illustrates how to use the lower_bound function.
//
// Functions:
// lower_bound : Return the lower bound within a range.
// disable warning C4786: symbol greater than 255 character,
// okay to ignore this warning
#pragma warning(disable: 4786)
#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>
using namespace std;
int main()
{
const int VECTOR_SIZE = 8 ;
// Define a template class vector of int
typedef vector<int > IntVector ;
//Define an iterator for template class vector of strings
typedef IntVector::iterator IntVectorIt ;
IntVector Numbers(VECTOR_SIZE) ;
IntVectorIt start, end, it, location ;
// Initialize vector Numbers
Numbers[0] = 4 ;
Numbers[1] = 10;
Numbers[2] = 70 ;
Numbers[3] = 10 ;
Numbers[4] = 30 ;
Numbers[5] = 69 ;
Numbers[6] = 96 ;
Numbers[7] = 100;
start = Numbers.begin() ; // location of first
// element of Numbers
end = Numbers.end() ; // one past the location
// last element of Numbers
//sort Numbers using the function object less<int>()
//lower_bound assumes that Numbers is sorted
//using the "compare" (less<int>() in this case)
//function
sort(start, end, less<int>()) ;
// print content of Numbers
cout << "Numbers { " ;
for(it = start; it != end; it++)
cout << *it << " " ;
cout << " }\n" << endl ;
// return the first location at which 10 can be inserted
// in Numbers
location = lower_bound(start, end, 10, less<int>()) ;
cout << "First location element 10 can be inserted in Numbers is: "
<< location - start << endl ;
}
Output
Numbers { 4 10 10 30 69 70 96 100 }
First location element 10 can be inserted in Numbers is: 1
Requirements
Header: <algorithm>