Iterator to last element in std::list

C++Stl

C++ Problem Overview

#include <list>
using std::list;

int main()
{
    list <int> n;
    n.push_back(1);
    n.push_back(2);
    n.push_back(3);
    
    list <int>::iterator iter = n.begin();
    std::advance(iter, n.size() - 1); //iter is set to last element
}

is there any other way to have an iter to the last element in list?

C++ Solutions

Solution 1 - C++

Yes, you can go one back from the end. (Assuming that you know that the list isn't empty.)

std::list<int>::iterator i = n.end();
--i;

Solution 2 - C++

Either of the following will return a std::list<int>::iterator to the last item in the list:

std::list<int>::iterator iter = n.end();
--iter;


std::list<int>::iterator iter = n.end();
std::advance(iter, -1);


// C++11
std::list<int>::iterator iter = std::next(n.end(), -1);


// C++11
std::list<int>::iterator iter = std::prev(n.end());

The following will return a std::list<int>::reverse_iterator to the last item in the list:

std::list<int>::reverse_iterator iter = std::list::rbegin();

Solution 3 - C++

With reverse iterators:

iter = (++n.rbegin()).base()

As a side note: this or Charles Bailey method have constant complexity while std::advance(iter, n.size() - 1); has linear complexity with list [since it has bidirectional iterators].

Solution 4 - C++

Take the end() and go one backwards.

list <int>::iterator iter = n.end();
cout << *(--iter);

Solution 5 - C++

std::list<int>::iterator iter = --n.end();
cout << *iter;

Solution 6 - C++

You could write your own functions to obtain a previous (and next) iterator from the given one (which I have used when I've needed "look-behind" and "look-ahead" with a std::list):

template <class Iter>
Iter previous(Iter it)
{
    return --it;
}

And then:

std::list<X>::iterator last = previous(li.end());

BTW, this might also be available in the boost library (next and prior).

Solution 7 - C++

list<int>n;
list<int>::reverse_iterator it;
int j;

for(j=1,it=n.rbegin();j<2;j++,it++)
cout<<*it;
Categories
Recommended C++ Solutions
Recommended Stl Solutions

Previous Solution:

When should one use dynamic keyword in c# 4.0?

C#DynamicC# 4.0Keyword

Next Solution:

Tail recursion in C++

C++RecursionG++Tail Recursion

Attributions

All content for this solution is sourced from the original question on Stackoverflow.

The content on this page is licensed under the Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.

Content TypeOriginal AuthorOriginal Content on Stackoverflow
QuestioncpxView Question on Stackoverflow
Solution 1 - C++CB BaileyView Answer on Stackoverflow
Solution 2 - C++Remy LebeauView Answer on Stackoverflow
Solution 3 - C++Eugen Constantin DincaView Answer on Stackoverflow
Solution 4 - C++Mitten.OView Answer on Stackoverflow
Solution 5 - C++B FaleyView Answer on Stackoverflow
Solution 6 - C++UncleBensView Answer on Stackoverflow
Solution 7 - C++Alexandru ManescuView Answer on Stackoverflow