adjacent_find

Algorithm

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

None

#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>
using namespace std;

 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;
 }

Program Output :

3 3 2 2

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

vector<int,allocator<int> >

instead of:

vector<int>

If your compiler does not support namespaces, then you do not need the using declaration for std.

find