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Duplicate: Choosing a STL container with uniqueness and which keeps insertion ordering
I'm looking for a data structure that acts like a set in that it doesn't allow duplicates to be inserted, but also knows the order in which the items were inserted. It would basically be a combination of a set and list/vector.
I would just use a list/vector and check for duplicates myself, but we need that duplicate verification to be fast as the size of the structure can get quite large.
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HashSet, LinkedHashSet and TreeSet are the implementations of Set interface which does not allow duplicate elements. In this tutorial we will see the differences between them. Fail-Fast Iterator is returned by HashSet, LinkedHashSet and TreeSet.
Unordered sets do not allow duplicates and are initialized using comma-delimited values enclosed in curly braces.
Summary. a List object can contain duplicate elements.
So, the conclusion, use std::unordered_set or std::unordered_map (if you need the key-value feature). And you don't need to check before doing the insertion, these are unique-key containers, they don't allow duplicates.
Take a look at Boost.MultiIndex. You may have to write a wrapper over this.
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A Boost.Bimap with the insertion order as an index should work (e.g. boost::bimap < size_t, Foo > ). If you are removing objects from the data structure, you will need to track the next insertion order value separately.
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