QMap but without sorting by key

Question

I need structure like QMap but without sorting on keys, so if I insert item there first I can count that this item will be before all others. And insert pair before or after specified element. Does Qt have such?

Answer 1

QMap is implemented as a tree, which means that the insertion order does not matter. It appears that you are looking for a queue . However, if you need a container which can be iterated in both insertion order and at the same time accessed through a specific key, then Qt has no such structure for you.

These could help you:

• A std::map that keep track of the order of insertion?
• Make Map Key Sorted According To Insert Sequence

Answer 2

I use a

QList<QPair<key,value>> 

to achieve this. But look up consumes more time as you will need to loop through the QList and use the QPair.first to look for the item you want.

edit: if you dont need it to interact with other API alot, you can use QVector to replace QList which is faster according to Qt official

Answer 3

Is QHash suitable for it?

QHash provides very similar functionality to QMap. The differences are:

• QHash provides faster lookups than QMap. (See Algorithmic Complexity for details.)
• When iterating over a QMap, the items are always sorted by key. With QHash, the items are arbitrarily ordered.