forward_list::begin() and forward_list::end() in C++ STL

Forward list in STL implements singly linked list. Introduced from C++11, forward list are useful than other containers in insertion, removal and moving operations (like sort) and allows time constant insertion and removal of elements.It differs from list by the fact that forward list keeps track of location of only next element while list keeps track to both next and previous elements.

forward_list::begin()

begin() function is used to return an iterator pointing to the first element of the forward list container. begin() function returns a bidirectional iterator to the first element of the container.

Syntax :

forwardlistname.begin()
Parameters :
No parameters are passed.
Returns :
This function returns a bidirectional
iterator pointing to the first element.

Examples:

Input  : myflist{1, 2, 3, 4, 5};
         myflist.begin();
Output : returns an iterator to the element 1

Input  : myflist{8, 7};
         myflist.begin();
Output : returns an iterator to the element 8

Errors and Exceptions

1. It has a no exception throw guarantee.
2. Shows error when a parameter is passed.

// CPP program to illustrate
// Implementation of begin() function
#include <forward_list>
#include <iostream>
using namespace std;

int main()
{
    // declaration of forward list container
    forward_list<int> myflist{ 1, 2, 3, 4, 5 };

    // using begin() to print list
    for (auto it = myflist.begin(); it != myflist.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output:

1 2 3 4 5

Time Complexity : O(1)

forward_list::end()

end() function is used to return an iterator pointing to the last element of the list container. end() function returns a bidirectional iterator to the last element of the container.

Syntax :

forwardlistname.end()
Parameters :
No parameters are passed.
Returns :
This function returns a bidirectional
iterator pointing to the last element.

Examples:

Input  : myflist{1, 2, 3, 4, 5};
         myflist.end();
Output : returns an iterator to the element 5

Input  : myflist{8, 7};
         myflist.end();
Output : returns an iterator to the element 7

Errors and Exceptions

1. It has a no exception throw guarantee.
2. Shows error when a parameter is passed.

// CPP program to illustrate
// Implementation of end() function
#include <forward_list>
#include <iostream>
using namespace std;

int main()
{
    // declaration of forward list container
    forward_list<int> myflist{ 1, 2, 3, 4, 5 };

    // using end() to print forward list
    for (auto it = myflist.begin(); it != myflist.end(); ++it)
        cout << ' ' << *it;
    return 0;
}

Output:

1 2 3 4 5

Time Complexity : O(1)

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