forward_list merge() in C++ STL

// CPP program to illustrate the
// forward_list::merge() function
#include <bits/stdc++.h>
using namespace std;

int main()
{
    forward_list<int> fl1 = { 12, 25, 31, 41 };
    forward_list<int> fl2 = { 10, 20, 30 };

    // merge two forward list
    fl1.merge(fl2);

    // print the contents of the forward list
    cout << "List contains following elements" << endl;
    for (auto it = fl1.begin(); it != fl1.end(); ++it)
        cout << *it << " ";

    return 0;
}

#include <bits/stdc++.h>
using namespace std;

// comparison function
bool cmp_fun(int a, int b)
{
    return a > b;
}

int main()
{
    forward_list<int> fl1 = { 41, 31, 25, 12 };
    forward_list<int> fl2 = { 30, 20, 10 };

    // merge two forward list
    fl1.merge(fl2, cmp_fun);

    // print the contents of the forward list
    cout << "List contains following elements" << endl;
    for (auto it = fl1.begin(); it != fl1.end(); ++it)
        cout << *it << " ";

    return 0;
}