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.

Time complexity

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.