# C++ Algorithm Library - inplace_merge() Function

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## Description

The C++ function std::algorithm::inplace_merge() merges two sorted sequence in-place. It uses operator< for comparison.

## Declaration

Following is the declaration for std::algorithm::inplace_merge() function form std::algorithm header.

### C++98

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

## Parameters

• first − Bidirectional iterator to the initial position of the first sequence.

• middle − Bidirectional iterator to the initial position of the second sequence.

• last − Bidirectional iterator to the past-the-end position of the second sequence.

None

## Exceptions

Throws exception if element comparison or swap operation or an operation on an iterator throws exception.

Please note that invalid parameters cause undefined behavior.

Linear.

## Example

The following example shows the usage of std::algorithm::inplace_merge() function.

```#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main(void) {
vector<int> v = {1, 3, 2, 4, 5};

inplace_merge(v.begin(), v.begin() + 2, v.end());

for (auto it = v.begin(); it != v.end(); ++it)
cout << *it << endl;

return 0;
}
```

Let us compile and run the above program, this will produce the following result −

```1
2
3
4
5
```
algorithm.htm