adjacent_find

Header

template<class ForwardIterator> inline
ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last) ;

The adjacent_find algorithm finds consecutive pairs of matching elements in a sequence. The adjacent_find algorithm returns an iterator referencing the first consecutive matching element in the range (first, last), or last if there are no such elements. Comparison is done using operator== in this non-predicate version of the algorithm.

template<class ForwardIterator, class BinaryPredicate> inline
ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last, BinaryPredicate binary_pred) ;

The adjacent_find algorithm finds consecutive pairs of matching elements in a sequence. adjacent_find returns an iterator referencing the first consecutive matching element in the range [first, last), or last if there are no such elements. Comparison is done using the binary_pred function in this version of the algorithm. The binary_pred function can be any user-defined function. You could also use one of the binary function objects provided by STL.

Samples

Sample for Non-Predicate Version

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <algorithm>
#include <iostream>

using namespace std;


void main()
{
    const int ARRAY_SIZE = 8 ;
    int IntArray[ARRAY_SIZE] = { 1, 2, 3, 4, 4, 5, 6, 7 } ;

    int *location ;   // stores the position for the first pair
                      // of matching consecutive elements.

    int i ;

    // print content of IntArray
    cout << "IntArray { " ;
    for(i = 0; i < ARRAY_SIZE; i++)
        cout << IntArray[i] << ", " ;
    cout << " }" << endl ;

    // Find the first pair of matching consecutive elements
    // in the range [first, last + 1)
    // This version performs matching using operator==
    location = adjacent_find(IntArray, IntArray + ARRAY_SIZE) ;

    //print the matching consecutive elements if any were found
    if (location != IntArray + ARRAY_SIZE)  // matching consecutive
                                            // elements found
        cout << "Found adjacent pair of matching elements: ("
        << *location << ", " << *(location + 1) << "), " <<
        "at location " << location - IntArray << endl;
    else         // no matching consecutive elements were found
        cout << "No adjacent pair of matching elements were found"
        << endl ;

}

Program Output

IntArray { 1, 2, 3, 4, 4, 5, 6, 7,  }
Found adjacent pair of matching elements: (4, 4), at location 3

Sample for Predicate Version

// disable warning C4786: symbol greater than 255 character,
// okay to ignore
#pragma warning(disable: 4786)

#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <vector>

using namespace std;


void main()
{
    const int VECTOR_SIZE = 5 ;

    // Define a template class vector of strings
    typedef vector<string > StringVector ;

    //Define an iterator for template class vector of strings
    typedef StringVector::iterator StringVectorIt ;

    StringVector NamesVect(VECTOR_SIZE) ;   //vector containing names

    StringVectorIt location ;   // stores the position for the
                                 // first pair of matching
                                 // consecutive elements.

    StringVectorIt start, end, it ;

    // Initialize vector NamesVect
    NamesVect[0] = "Aladdin" ;
    NamesVect[1] = "Jasmine" ;
    NamesVect[2] = "Mickey" ;
    NamesVect[3] = "Minnie" ;
    NamesVect[4] = "Goofy" ;

    start = NamesVect.begin() ;   // location of first
                                  // element of NamesVect

    end = NamesVect.end() ;       // one past the location
                                  // last element of NamesVect

    // print content of NamesVect
    cout << "NamesVect { " ;
    for(it = start; it != end; it++)
        cout << *it << ", " ;
    cout << " }\n" << endl ;

    // Find the first name that is lexicographically greater
    // than the following name in the range [first, last + 1).
    // This version performs matching using binary predicate
    // function greater<string>
    location = adjacent_find(start, end, greater<string>()) ;

    // print the first pair of strings such that the first name is
    // lexicographically greater than the second.
    if (location != end)
        cout << "(" << *location << ", " << *(location + 1) << ")"
        << " the first pair of strings in NamesVect such that\n"
        << "the first name is lexicographically greater than"
        << "the second\n" << endl ;
    else
        cout << "No consecutive pair of strings found such that\n"
        << "the first name is lexicographically greater than "
        << "the second\n" << endl ;

}

Program Output

NamesVect { Aladdin, Jasmine, Mickey, Minnie, Goofy,  }

(Minnie, Goofy) the first pair of strings in NamesVect such that
the first name is lexicographically greater than the second