# C++ Algorithm Library - is_sorted() Function

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## Description

The C++ function std::algorithm::is_sorted() tests whether range is sorted or not. It uses operator< for comparision.

## Declaration

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

### C++11

```template <class ForwardIterator>
bool is_sorted (ForwardIterator first, ForwardIterator last);
```

## Parameters

• first − Forward iterator to the initial position.

• last − Forward iterator to the final position.

## Return value

Returns true if range is sorted otherwise returns false.

## Exceptions

Throws exception if either the element comparison 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::is_sorted() function.

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

using namespace std;

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

result = is_sorted(v.begin(), v.end());

if (result == true)
cout << "Vector elements are sorted in ascending order." << endl;

v[0] = 10;

result = is_sorted(v.begin(), v.end());

if (result == false)
cout << "Vector elements are not sorted in ascending order." << endl;

return 0;
}
```

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

```Vector elements are sorted in ascending order.
Vector elements are not sorted in ascending order.
```
algorithm.htm
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