multiset emplace_hint() function in C++ STL

The multiset::emplace_hint() is a built-in function in C++ STL which inserts a new element in the multiset. A position is passed in the parameter of the function which acts as a hint from where the searching operation starts before inserting the element at its current position. The position only helps the process to get faster, it does not decide where the new element is to be inserted. The new element is inserted following the property of the multiset container only.

Syntax:

multiset_name.emplace_hint(iterator position, value)

Parameters: The function accepts two mandatory parameters which are described below:

• position: This parameter acts as a hint from where the searching operation is done before inserting the element at its current position. The position only helps the process to be faster, it does not decide where the new element is to be inserted. The new element is inserted following the property of the multiset container only.
• value: This specifies the element to inserted in the multiset container.

Return Value: The function returns an iterator pointing to the position where the insertion is done.

Below program illustrates the above function.

Program 1:

// CPP program to demonstrate the
// multiset::emplace_hint() function
#include <bits/stdc++.h>
using namespace std;
int main()
{

    multiset<int> s;
    auto it = s.emplace_hint(s.begin(), 1);

    // stores the position of 2's insertion
    it = s.emplace_hint(it, 2);

    // fast step as it directly
    // starts the search step from
    // position where 2 was last inserted
    s.emplace_hint(it, 4);

    // this is a slower step as
    // it starts checking from the
    // position where 4 was inserted
    // but 3 is to be inserted before 4
    s.emplace_hint(it, 3);

    // prints the multiset elements
    for (auto it = s.begin(); it != s.end(); it++)
        cout << *it << " ";

    return 0;
}

Output:

1 2 3 4

Program 2:

// CPP program to demonstrate the
// multiset::emplace_hint() function
#include <bits/stdc++.h>
using namespace std;
int main()
{

    multiset<int> s;
    auto it = s.emplace_hint(s.begin(), 1);

    // stores the position of 2's insertion
    it = s.emplace_hint(it, 2);

    // fast step as it directly
    // starts the search step from
    // position where 2 was last inserted
    s.emplace_hint(it, 4);

    // this is a slower step as
    // it starts checking from the
    // position where 4 was inserted
    // but 3 is to be inserted before 4
    s.emplace_hint(it, 3);

    // slower steps
    s.emplace_hint(s.begin(), 6);
    s.emplace_hint(s.begin(), 6);
    s.emplace_hint(s.begin(), 6);
    s.emplace_hint(s.begin(), 6);

    // prints the multiset elements
    for (auto it = s.begin(); it != s.end(); it++)
        cout << *it << " ";

    return 0;
}

Output:

1 2 3 4 6 6 6 6