I dont want to use threads
Threads? Nothing to do with it.
is there any other data structures available for faster execution or my choice is correct ?
There is little faster than a directly indexed, contiguous block of memory like QVector. If you do not know the precise size ahead of schedule but can take a educated guess then use that in reserve().

Rather than fixate on a data structure panacea why not do the work to isolate exactly where your algorithm and storage are really spending most of their time. Then you have some idea what it is you are trying to optimise.