adjacent_find

     Algorithm

Find the first adjacent pair of elements in a sequence that are equivalent.

Contents

• Synopsis
• Description
• Complexity
• Example
• Warning
• See Also

#include <algorithm>

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

There are two versions of the adjacent_find algorithm. The first finds equal adjacent elements in the sequence defined by iterators first and last and returns an iterator i pointing to the first of the equal elements. The second version lets you specify your own binary function to test for a condition. It returns an iterator i pointing to the first of the pair of elements that meet the conditions of the binary function. In other words, adjacent_find returns the first iterator i such that both i and i + 1 are in the range [first, last) for which one of the following conditions holds:

  *i  ==  *(i  +  1)

or

pred(*i,*(i  +  1))  == true

If adjacent_find does not find a match, it returns last.

adjacent_find performs exactly find(first,last,value) - first applications of the corresponding predicate.

//
// find.cpp
//
#include <vector>
#include <algorithm>
#include <iostream.h>
 int main()
 {
   typedef vector<int>::iterator iterator;
   int d1[10] = {0,1,2,2,3,4,2,2,6,7}; 
   // Set up a vector
   vector<int> v1(d1,d1 + 10);
   // Try find  
   iterator it1 = find(v1.begin(),v1.end(),3);
   // Try find_if
   iterator it2 = 
      find_if(v1.begin(),v1.end(),bind1st(equal_to<int>(),3));
   // Try both adjacent_find variants
   iterator it3 = adjacent_find(v1.begin(),v1.end());
   iterator it4 = 
      adjacent_find(v1.begin(),v1.end(),equal_to<int>());
   // Output results
   cout << *it1 << " " << *it2 << " " << *it3 << " " 
        << *it4 << endl;
   return 0;
 }
Output :
3 3 2 2

If your compiler does not support default template parameters then you need to always supply the Allocator template argument. For instance you'll have to write:

vector<int,allocator>

instead of:

vector<int>

find