Apache C++ Standard Library Reference Guide

Library:  Algorithms

`Function`

No Entries

### Summary

An algorithm that finds the first adjacent pair of equivalent elements in a sequence

### Synopsis

```#include <algorithm>

namespace std {
template <class ForwardIterator>
ForwardIterator
ForwardIterator finish);

template <class ForwardIterator, class BinaryPredicate>
ForwardIterator
BinaryPredicate binary_pred);
}
```

### Description

There are two variations of the adjacent_find() algorithm. The first finds equal adjacent elements in the sequence defined by iterators start and finish and returns an iterator i pointing to the first of the equal elements. The second variation lets you specify a binary function object to test for a condition. The algorithm 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 where both i and i + 1 are in the range [start, finish) that meets one of the following conditions:

*i == *(i + 1)

or

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

If adjacent_find() does not find a match, it returns finish.

### Complexity

adjacent_find() performs exactly find(start,finish,value) - start applications of the corresponding predicate.

### Example

```//
//  find.cpp
//

#include <vector>      // for vector
#include <algorithm>   // for adjacent_find, find
#include <functional>  // for bind1st, equal_to
#include <iostream>    // for cout, endl

int main ()
{
// Typedef for convenience.
typedef std::vector<int, std::allocator<int> > Vector;

const Vector::value_type arr[] = { 0, 1, 2, 2, 3,
4, 2, 2, 6, 7 };

// Set up a vector.
const Vector v1 (arr, arr + sizeof arr / sizeof *arr);

// Try find.
Vector::const_iterator it = std::find (v1.begin (),
v1.end (), 3);

std::cout << *it << ' ';

// Try find_if.
it = std::find_if (v1.begin (), v1.end (),
std::bind1st (std::equal_to<Vector::value_type>(),
3));

std::cout << *it << ' ';

it = std::adjacent_find (v1.begin (), v1.end ());

std::cout << *it << ' ';

it = std::adjacent_find (v1.begin (), v1.end (),
std::equal_to<Vector::value_type>());

std::cout << *it << std::endl;

return 0;
}

Program Output:
```
```3 3 2 2
```