# Man Page inplace_merge.3

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

```

## NAME

```     inplace_merge

- Merges two sorted sequences into one.

```

## SYNOPSIS

```     #include <algorithm>
template <class BidirectionalIterator>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last);

template <class BidirectionalIterator, class Compare>
void inplace_merge(BidirectionalIterator first,
BidirectionalIterator middle,
BidirectionalIterator last,
Compare comp);

```

## DESCRIPTION

```     The inplace_merge algorithm merges  two  sorted  consecutive
ranges  [first,  middle)  and  [middle,  last), and puts the
result of the merge into the range [first, last). The  merge
is  stable,  which  means  that  if  the  two ranges contain
equivalent elements,  the  elements  from  the  first  range
always precede the elements from the second.

There are two versions of the inplace_merge  algorithm.  The
first version uses the less than operator (operator<) as the
default for comparison, and the  second  version  accepts  a
third argument that specifies a comparison operator.

```

## COMPLEXITY

```     When enough additional memory  is  available,  inplace_merge
does  at  most  (last  - first) - 1 comparisons. If no addi-
tional memory is available, an algorithm with O(NlogN)  com-
plexity (where N is equal to last-first) may be used.

```

## EXAMPLE

```     //
// merge.cpp
//
#include <algorithm>
#include <vector>
#include <functional>
#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.

```

```     merge