# C++ Algorithm Library - iter_swap() Function

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## Description

The C++ function std::algorithm::iter_swap() exchange values of objects pointed by two iterators. It uses function swap (unqualified) to exchange the elements.

## Declaration

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

### C++98

```template <class ForwardIterator1, class ForwardIterator2>
void iter_swap (ForwardIterator1 a, ForwardIterator2 b);
```

## Parameters

• a − First forward iterator object.

• b − Second forward iterator object.

None

## Exceptions

Throws exception if swap function throws an exception.

Please note that invalid parameters cause undefined behavior.

Constant.

## Example

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

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

using namespace std;

int main(void) {
vector<int> v1 = {1, 2, 3, 4, 5};
vector<int> v2 = {10, 20, 30, 40, 50};

iter_swap(v1.begin(), v2.begin());
iter_swap(v1.begin() + 1, v2.begin() + 2);

cout << "Vector v2 contains following elements" << endl;

for (auto it = v2.begin(); it != v2.end(); ++it)
cout << *it << endl;

return 0;
}
```

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

```Vector v2 contains following elements
1
20
2
40
50
```
algorithm.htm