iterators after element deletion in cpp

Question

In c++ , what happens to the iterators when an element is added or deleted.

For example, vector is :{1,2,3,4,5,6} and suppose two iterators a and b point to element '2', and '5'. If I delete 3rd item i.e. delete '3', what will the iterators be pointing to ?

And if the iterator points to the last element, and that element gets deleted, will it cause error? I need to implement this code, where the elements are randomly deleted, i wanted to know the best /suitable data structure in which references doesn't change after the insertion ordeletion.

A nice summary: [iterator invalidation](https://en.cppreference.com/w/cpp/container#Iterator_invalidation). — Eljay, Aug 15 '20 at 15:11
It'll not cause an error (unless you're lucky) but modifying a collection while holding in a iterator invalidates the iterator. Doing anything with it after that point is undefined behaviour — Ted Klein Bergman, Aug 15 '20 at 15:11

Suniti Jain · Accepted Answer · 2020-08-15T15:58:31.593

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i guess what you are looking for is iterator invalidation: https://www.geeksforgeeks.org/iterator-invalidation-cpp/#:~:text=Resizing-,a.,it%20is%20supposed%20to%20point. check this link.

The summary is: if you delete element in vector, all the iterators pointing to the elements after deleted element gets changed. The iterator to the deleted element gets invalidated. Sometimes the program crashes and sometimes it just shows unpredictable answer.

the rules are different for other containers/sequence.

edited Aug 15 '20 at 15:58

answered Aug 15 '20 at 15:08

Suniti Jain

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That website offers articles of extremely poor quality and better be avoided by anyone who learns C++. – Evg Aug 15 '20 at 15:13
this link was useful for me, i agree with you. Indeed the content is not satisfactory. – Suniti Jain Aug 15 '20 at 15:21
@Evg it's useful as a quick reference for certain common use cases of the STL. But yeah – Makogan Aug 15 '20 at 15:23
@Makogan true, it nice for quick refrences – Suniti Jain Aug 15 '20 at 15:24

iterators after element deletion in cpp

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