list splice() function in C++ STL

The list::splice() is a built-in function in C++ STL which is used to transfer elements from one list to another. The splice() function can be used in three ways: 

1. Transfer all the elements of list x into another list at some position.
2. Transfer only the element pointed by i from list x into the list at some position.
3. Transfers the range [first, last) from list x into another list at some position.

Syntax

list1_name.splice (iterator position, list2)
                or 
list1_name.splice (iterator position, list2, iterator i)
                or 
list1_name.splice (iterator position, list2, iterator first, iterator last)

Parameters: The function accepts four parameters which are specified as below: 

• position – Specifies the position where the elements are to be transferred.
• list2 – It specifies a list object of the same type which is to be transferred.
• i – It specifies an iterator to the position of an element in list2 which is to be transferred.
• first, last – Iterators specifying a range of elements in list2 which is to be transferred in list1. The range includes all the elements between first and last, including the element pointed by first but not the one pointed by last.

Return value: This function does not returns anything. 

Program 1: Transfer all the elements of the list. 

C++

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

int main()
{
    // initializing lists
    list<int> l1 = { 1, 2, 3 };
    list<int> l2 = { 4, 5 };
    list<int> l3 = { 6, 7, 8 };

    // transfer all the elements of l2
    l1.splice(l1.begin(), l2);

    // at the beginning of l1
    cout << "list l1 after splice operation" << endl;
    for (auto x : l1)
        cout << x << " ";

    // transfer all the elements of l1
    l3.splice(l3.end(), l1);

    // at the end of l3
    cout << "\nlist l3 after splice operation" << endl;
    for (auto x : l3)
        cout << x << " ";
    return 0;
}

Output

list l1 after splice operation
4 5 1 2 3 
list l3 after splice operation
6 7 8 4 5 1 2 3 

Time Complexity: O(1)
Auxiliary Space: O(1)

Program 2: Transfer a single element.

CPP

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

int main()
{
    // initializing lists and iterator
    list<int> l1 = { 1, 2, 3 };
    list<int> l2 = { 4, 5 };
    list<int>::iterator it;

    // Iterator pointing to 4
    it = l2.begin();

    // transfer 4 at the end of l1
    l1.splice(l1.end(), l2, it);

    cout << "list l1 after splice operation" << endl;
    for (auto x : l1)
        cout << x << " ";
    return 0;
}

Output

list l1 after splice operation
1 2 3 4 

Time Complexity: O(1)
Auxiliary Space: O(1)

Program 3: Transfer a range of elements.

CPP

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

int main()
{
    // initializing lists and iterator
    list<int> l1 = { 1, 2, 3, 4, 5 };
    list<int> l2 = { 6, 7, 8 };
    list<int>::iterator it;

    // iterator pointing to 1
    it = l1.begin();

    // advance the iterator by 2 positions
    advance(it, 2);

    // transfer 3, 4 and 5 at the
    // beginning of l2
    l2.splice(l2.begin(), l1, it, l1.end());

    cout << "list l2 after splice operation" << endl;
    for (auto x : l2)
        cout << x << " ";
    return 0;
}

Output

list l2 after splice operation
3 4 5 6 7 8 

Time Complexity: O(n)
Auxiliary Space: O(1)