C++ <forward_list> - sort() Function

The C++ forward_list::sort function is used to sort the elements of the forward_list container. The comparison produces a strict weak ordering of the elements.

Syntax

C++11

//version 1
void sort();
 
//version 2
template <class Compare>
void sort (Compare comp);

Parameters

comp Specify a binary predicate that takes two elements of the forward_list as arguments and returns a bool. It follows the strict weak ordering to order the elements.

Return Value

None.

Time Complexity

Linearithmic i.e, Θ(nlog(n)).

Example:

In the example below, the forward_list::sort function is used to sort the elements of the given forward_list called flist.

#include <iostream>
#include <forward_list>
using namespace std;
 
int main (){
  forward_list<int> flist{33, 7, 45, -12, 25, 75};
  forward_list<int>::iterator it;

  cout<<"flist contains: ";
  for(it = flist.begin(); it != flist.end(); it++)
    cout<<*it<<" ";

  //sort elements of the forward_list
  flist.sort();
  
  cout<<"\nflist contains: ";
  for(it = flist.begin(); it != flist.end(); it++)
    cout<<*it<<" ";

  return 0;
}

The output of the above code will be:

flist contains: 33 7 45 -12 25 75 
flist contains: -12 7 25 33 45 75

Example:

Here, the forward_list is sorted by following: 1) alphabetically and 2) according to the length of the element. Consider the example below:

#include <iostream>
#include <forward_list>
using namespace std;
 
bool compare_length (string s1, string s2) {
  return ( s1.length() < s2.length() );
}

int main () {
  forward_list<string> flist{"Jo", "John", "Marry", "Kim", "Chandan"};
  forward_list<string>::iterator it;

  cout<<"flist contains: ";
  for(it = flist.begin(); it != flist.end(); it++)
    cout<<*it<<" ";

  //sort elements of the forward_list alphabetically
  flist.sort();
  
  cout<<"\nflist contains: ";
  for(it = flist.begin(); it != flist.end(); it++)
    cout<<*it<<" ";

  //sort elements of the forward_list according 
  //to length of the element
  flist.sort(compare_length);
  
  cout<<"\nflist contains: ";
  for(it = flist.begin(); it != flist.end(); it++)
    cout<<*it<<" ";

  return 0;
}

The output of the above code will be:

flist contains: Jo John Marry Kim Chandan 
flist contains: Chandan Jo John Kim Marry 
flist contains: Jo Kim John Marry Chandan

❮ C++ <forward_list> Library