reading from a file

[jacek]

Sorry, but the solutions with esamples of some posts before is different from what you said here above??

No, that's the first step, which allows you to save some time.

With solution with examples where Have I the vectors? Where do I call sort() ?

Instead of starting the merge sort algorithm with blockSize = 1, you can start it with blockSize = 256000, but you'll need a file that contains sorted blocks of 256000 lines. That's where you are going to use the vector and sort().

• f := [A, B].
• fileId := 0.
• while not end of file X:
  
  • vector := read 256000 lines from file X,
  • sort vector,
  • write vector to file f[fileId],
  • fileId := 1 - fileId.
• blockSize := 256000.
• go to 3 from post #23.

Merge sort is one of the basic algorithms that every programmer should know. If you need more explanations, see Algorithms + Data Structures = Programs by Niklaus Wirth.