Sorting Operations in header algorithm in C++

By Timsal Zehra Rizvi

The Packet explains the sorting operations defined in the header algorithm with an example of each to have a better understanding.

Sorting operations:

1)is_sorted(): The function checks and returns true if the given sequence is sorted into ascending order else returns false.

Syntax: is_sorted (Iterator pointing to first, iterator pointing to last );

Example:

#include 
#include 
using namespace std;
int main()
{
    int arr[] = { 5, 8, 9, 2 };
    int n1=(sizeof(arr) / sizeof(arr[0]))-1;
    int n2=(sizeof(arr) / sizeof(arr[0]));
    if (is_sorted(arr, arr + n1))
    {
        cout << "The given array is sorted in the given range"<<endl;
    } 
    if(!is_sorted(arr,arr+n2)) 
    {
        cout << "The given array is not sorted in the given range"<<endl;
    }
}

2)is_sorted_until(): The function checks and returns the first unsorted element in the given sequence and if the sequence is sorted then returns an iterator pointing to the last.

Syntax: is_sorted_until (Iterator pointing to first, iterator pointing to last );

Example:

#include 
#include 
using namespace std;
int main()
{
    int arr[] = {5,8,9,2};
    int n=(sizeof(arr) / sizeof(arr[0]));
    int* x=is_sorted_until(arr, arr + n);
    cout<< *x;
}

3)sort() :sorts the given sequence into ascending order

Syntax: sort(Iterator pointing to first, iterator pointing to last) //for ascending order

sort(Iterator pointing to first , iterator pointing to last, greater()); //for descending order

Example:

#include
#include<bits/stdc++.h>
using namespace std;
  
int main()
{
    int arr[] = {5,8,9,2};
    int n = sizeof(arr) / sizeof(arr[0]);
    sort(arr, arr + n);    // For descending order - sort(arr, arr + n, greater());
    cout <<"Sorted array is:"<<endl;
    for (int i = 0; i < n; ++i)
        cout << arr[i] << " ";
return 0;
}

4) partial_sort(): sorts the first n elements of a range in such a way that half of the sequence is sorted and the other half is unsorted.

Syntax: partial_sort(Iterator pointing to first, iterator pointing to the middle element, iterator pointing to last)

Example:

#include 
#include 
#include 
using namespace std;
int main()
{
    vector arr = {  5,8,5,9,10 };
    vector::iterator i;
    partial_sort(arr.begin(), arr.begin() + 3, arr.end());
     for (i = arr.begin(); i != arr.end(); ++i) {
        cout << *i << " ";
    }