boost::algorithm::is_sorted() in C++ library

The is_sorted() function in C++ boost library is found under the header ‘boost/algorithm/cxx11/is_sorted.hpp’ which tests if the given sequence is sorted or not according to some given criteria which is specified in the predicate. If no comparison predicate is specified, then std::less is used to see if the sequence is non-decreasing.

Syntax:

bool is_sorted ( ForwardIterator first, ForwardIterator last, Pred p )
or
bool is_sorted ( ForwardIterator first, ForwardIterator last )
or
bool is_sorted ( const Range &r, Pred p )
or
bool is_sorted ( const Range &r )

Parameters: The function accepts parameters as described below:

  • first: It specifies the input iterators to the initial positions in a sequence.
  • second: It specifies the input iterators to the final positions in a sequence.
  • p: It specifies the comparison predicate if specified.
  • r: It specifies the given range completely.

Return Value: The function returns true if the complete sequence is sorted according to the given criteria, else it returns false.

Below is the implementation of the above approach:

Program-1:

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// C++ program to implement the
// above mentioned function
  
#include <bits/stdc++.h>
#include <boost/algorithm/cxx11/is_sorted.hpp>
using namespace std;
  
// Drivers code
int main()
{
  
    // Declares the sequence with
    int c[] = { 1, 2, 6, 8 };
  
    // Run the function
    bool ans = boost::algorithm::is_sorted(c);
  
    // Condition to check
    if (ans == 1)
        cout << "sorted";
    else
        cout << "not sorted";
    return 0;
}

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Output:

sorted

Program-2:

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#include <bits/stdc++.h>
#include <boost/algorithm/cxx11/is_sorted.hpp>
using namespace std;
  
// Drivers code
int main()
{
  
    // Declares the sequence with
    int c[] = { 1, 2, 10, 8 };
  
    // Run the function
    bool ans
        = boost::algorithm::is_sorted(c, c + 3);
  
    // Condition to check
    if (ans == 1)
        cout << "sorted till 3rd index";
    else
        cout << "not sorted till 3rd index";
    return 0;
}

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Output:

sorted till 3rd index

Reference: https://www.boost.org/doc/libs/1_70_0/libs/algorithm/doc/html/the_boost_algorithm_library/CXX11/is_sorted.html



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