# unique_copy

Copies elements from a source range into a destination range except for the duplicate elements that are adjacent to each other.

```
template<class InputIterator, class OutputIterator>
OutputIterator unique_copy(
InputIterator _First,
InputIterator _Last,
OutputIterator _Result
);
template<class InputIterator, class OutputIterator, class BinaryPredicate>
OutputIterator unique_copy(
InputIterator _First,
InputIterator _Last,
OutputIterator _Result,
BinaryPredicate _Comp,
);
```

## Parameters

_First

A forward iterator addressing the position of the first element in the source range to be copied._Last

A forward iterator addressing the position one past the final element in the source range to be copied._Result

An output iterator addressing the position of the first element in the destination range that is receiving the copy with consecutive duplicates removed._Comp

User-defined predicate function object that defines the condition to be satisfied if two elements are to be taken as equivalent. A binary predicate takes two arguments and returns**true**when satisfied and**false**when not satisfied.

## Return Value

An output iterator addressing the position one past the final element in the destination range that is receiving the copy with consecutive duplicates removed.

## Remarks

Both forms of the algorithm remove the second duplicate of a consecutive pair of equal elements.

The operation of the algorithm is stable so that the relative order of the undeleted elements is not changed.

The ranges referenced must be valid; all pointers must be dereferenceable and within a sequence the last position is reachable from the first by incrementation.

The complexity is linear, requiring (_Last – _First) comparisons.

**unique_copy** has two related forms:

For information on how these functions behave, see Checked Iterators.

## Example

```
// alg_unique_copy.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>
#include <ostream>
using namespace std;
// Return whether modulus of elem1 is equal to modulus of elem2
bool mod_equal ( int elem1, int elem2 ) {
if ( elem1 < 0 )
elem1 = - elem1;
if ( elem2 < 0 )
elem2 = - elem2;
return elem1 == elem2;
};
int main() {
vector <int> v1;
vector <int>::iterator v1_Iter1, v1_Iter2,
v1_NewEnd1, v1_NewEnd2;
int i;
for ( i = 0 ; i <= 1 ; i++ ) {
v1.push_back( 5 );
v1.push_back( -5 );
}
int ii;
for ( ii = 0 ; ii <= 2 ; ii++ )
v1.push_back( 4 );
v1.push_back( 7 );
int iii;
for ( iii = 0 ; iii <= 5 ; iii++ )
v1.push_back( 10 );
cout << "Vector v1 is\n ( " ;
for ( v1_Iter1 = v1.begin( ) ; v1_Iter1 != v1.end( ) ; v1_Iter1++ )
cout << *v1_Iter1 << " ";
cout << ")." << endl;
// Copy first half to second, removing consecutive duplicates
v1_NewEnd1 = unique_copy ( v1.begin ( ) , v1.begin ( ) + 8, v1.begin ( ) + 8 );
cout << "Copying the first half of the vector to the second half\n "
<< "while removing adjacent duplicates gives\n ( " ;
for ( v1_Iter1 = v1.begin( ) ; v1_Iter1 != v1_NewEnd1 ; v1_Iter1++ )
cout << *v1_Iter1 << " ";
cout << ")." << endl;
int iv;
for ( iv = 0 ; iv <= 7 ; iv++ )
v1.push_back( 10 );
// Remove consecutive duplicates under the binary prediate mod_equals
v1_NewEnd2 = unique_copy ( v1.begin ( ) , v1.begin ( ) + 14,
v1.begin ( ) + 14 , mod_equal );
cout << "Copying the first half of the vector to the second half\n "
<< " removing adjacent duplicates under mod_equals gives\n ( " ;
for ( v1_Iter2 = v1.begin( ) ; v1_Iter2 != v1_NewEnd2 ; v1_Iter2++ )
cout << *v1_Iter2 << " ";
cout << ")." << endl;
}
```

## Output

```
Vector v1 is
( 5 -5 5 -5 4 4 4 7 10 10 10 10 10 10 ).
Copying the first half of the vector to the second half
while removing adjacent duplicates gives
( 5 -5 5 -5 4 4 4 7 5 -5 5 -5 4 7 ).
Copying the first half of the vector to the second half
removing adjacent duplicates under mod_equals gives
( 5 -5 5 -5 4 4 4 7 5 -5 5 -5 4 7 5 4 7 5 4 7 ).
```

## Requirements

**Header:** <algorithm>

**Namespace:** std