What is the partial_sort() function in C++?

In this shot, we will discuss how to use the partial_sort() function in C++. It is present in the <algorithm> library.

The partial_sort() function is used for sorting a part of the range, not the entire range.

Parameters

The partial_sort() function takes the following parameters:

  • Begin: This is a random access iterator pointing to the first element in the range.
  • End: This is a random access iterator pointing to the first element in the range.
  • Boundary: This is a random access iterator pointing to the upper boundary element in the range [Begin, End), that is used as the upper boundary for the elements to be sorted.
  • Pred: This is a user-defined function which returns true if the 2 arguments passed are in order (it follows strict weak ordering).

Return

The partial_sort() function doesn’t return anything.

Code

Let’s see the code snippet below.

#include<iostream>
#include<algorithm> 
#include<vector>
using namespace std;
bool pred(int x, int y)
{
return (x<y);
}
int main()
{
vector<int> vect = { 12, 15, 9, 7, 84, 74 },v(4);
vector<int>::iterator ip;
partial_sort(vect.begin(), vect.begin() + 4, vect.end(), pred);
cout<<"The resultant vector after using partial_sort() is: ";  
for (ip = vect.begin(); ip != vect.end(); ip++) 
cout << *ip << " ";
cout<<endl;
return 0;
}

Explanation

  • In lines 1 to 3, we import the required libraries.
  • In lines 5 to 8, we define a function to check whether the first element in the argument is less than the second element in the argument.
  • In line 10, we make a main function.
  • In line 12, we initialize a vector and declare another vector to store the copy.
  • In line 13, we declare an iterator to a vector.
  • In line 14, we use the partial_sort() method to sort a subrange of the entire initialized vector.
  • In line 16, we display a message regarding the upcoming modified vector.
  • In lines 17 and 18, we use a loop to access and display the elements with the help of an iterator of the modified vector after using the partial_sort() function on the vector.

In this way, we can use the partial_sort() function in C++.

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