# Man Page merge.3

```
Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

```

## NAME

```     merge

- Merges two sorted sequences into a third sequence.

```

## SYNOPSIS

```     #include <algorithm>
template <class InputIterator1, class InputIterator2,
class OutputIterator>
OutputIterator
merge(InputIterator first1, InputIterator1 last1,
InputIterator2 first2, InputIterator last2,
OutputIterator result);

template <class InputIterator1, class InputIterator2,
class OutputIterator, class Compare>
OutputIterator
merge(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator last2,
OutputIterator result, Compare comp);

```

## DESCRIPTION

```     The merge algorithm merges two sorted  sequences,  specified
by  [first1,  last1)  and [first2, last2), into the sequence
specified by [result, result + (last1 - first1) +  (last2  -
first2)).  The first version of the merge algorithm uses the
less than operator  (<)  to  compare  elements  in  the  two
sequences.  The  second version uses the comparison function
included in the function call. If a comparison  function  is
included,  merge  assumes  that  both  sequences were sorted
using that comparison function.

The merge is stable. This means that  if  the  two  original
sequences contain equivalent elements, the elements from the
first sequence always precede the matching elements from the
second  in the resulting sequence. The size of the result of
a merge is equal to the sum of the sizes of the two argument
sequences.  merge returns an iterator that points to the end
of the resulting sequence (in other words, result + (last1 -
first1) + (last2 -first2)). The result of merge is undefined
if the resulting range overlaps with either of the  original
ranges.
merge assumes that there are at least  (last1  -  first1)  +
(last2  -  first2)  elements following result, unless result
has been adapted by an insert iterator.

```

## COMPLEXITY

```     At most (last - first1) + (last2 - first2) -  1  comparisons
are performed.

```

## EXAMPLE

```     //
// merge.cpp
//
#include <algorithm>
#include <vector>
#include <iostream>
using namespace std;

int main()
{
int d1[4] = {1,2,3,4};
int d2[8] = {11,13,15,17,12,14,16,18};

// Set up two vectors
vector<int> v1(d1,d1 + 4), v2(d1,d1 + 4);
// Set up four destination vectors
vector<int> v3(d2,d2 + 8),v4(d2,d2 + 8),
v5(d2,d2 + 8),v6(d2,d2 + 8);
// Set up one empty vector
vector<int> v7;

// Merge v1 with v2
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
v3.begin());
// Now use comparator
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),v4.begin(),
less<int>());

// In place merge v5
vector<int>::iterator mid = v5.begin();
inplace_merge(v5.begin(),mid,v5.end());
// Now use a comparator on v6
mid = v6.begin();
inplace_merge(v6.begin(),mid,v6.end(),less<int>());

// Merge v1 and v2 to empty vector using insert iterator
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
back_inserter(v7));

// Copy all cout
ostream_iterator<int,char> out(cout," ");
copy(v1.begin(),v1.end(),out);
cout << endl;
copy(v2.begin(),v2.end(),out);
cout << endl;
copy(v3.begin(),v3.end(),out);
cout << endl;
copy(v4.begin(),v4.end(),out);
cout << endl;
copy(v5.begin(),v5.end(),out);
cout << endl;
copy(v6.begin(),v6.end(),out);
cout << endl;
copy(v7.begin(),v7.end(),out);
cout << endl;

// Merge v1 and v2 to cout
merge(v1.begin(),v1.end(),v2.begin(),v2.end(),
ostream_iterator<int,char>(cout," "));
cout << endl;

return 0;
}

Program Output

1 2 3 4
1 2 3 4
1 1 2 2 3 3 4 4
1 1 2 2 3 3 4 4
11 12 13 14 15 16 17 18
11 12 13 14 15 16 17 18
1 1 2 2 3 3 4 4
1 1 2 2 3 3 4 4

```

## WARNINGS

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

vector<int,allocator<int> >

vector<int>

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

```

```     Containers, inplace_merge

```