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Sort in C++ Standard Template Library (STL)

  • Difficulty Level : Easy
  • Last Updated : 31 Aug, 2021
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Sorting is one of the most basic functions applied to data. It means arranging the data in a particular fashion, which can be increasing or decreasing. There is a builtin function in C++ STL by the name of sort(). 
This function internally uses IntroSort. In more details it is implemented using hybrid of QuickSort, HeapSort and InsertionSort.By default, it uses QuickSort but if QuickSort is doing unfair partitioning and taking more than N*logN time, it switches to HeapSort and when the array size becomes really small, it switches to InsertionSort. 

The prototype for sort is : 

sort(startaddress, endaddress)

startaddress: the address of the first 
              element of the array
endaddress: the address of the next 
            contiguous location of the 
            last element of the array.
So actually sort() sorts in the 
range of [startaddress,endaddress)


// C++ program to sort an array
#include <algorithm>
#include <iostream>
using namespace std;
void show(int a[], int array_size)
    for (int i = 0; i < array_size; ++i)
        cout << a[i] << " ";
// Driver code
int main()
    int a[] = { 1, 5, 8, 9, 6, 7, 3, 4, 2, 0 };
    // size of the array
    int asize = sizeof(a) / sizeof(a[0]);
    cout << "The array before sorting is : \n";
    // print the array
    show(a, asize);
      // sort the array
    sort(a, a + asize);
    cout << "\n\nThe array after sorting is :\n";
    // print the array after sorting
    show(a, asize);
    return 0;
The array before sorting is : 
1 5 8 9 6 7 3 4 2 0 

The array after sorting is :
0 1 2 3 4 5 6 7 8 9 

Refer std::sort() for more details.

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