[Tutor] Sorting large numbers of co-ordinate pairs

Dinesh B Vadhia dineshbvadhia at hotmail.com
Thu Mar 12 14:43:49 CET 2009

Have a large number (> 1bn) of integer co-ordinates (i, j).  The i are ordered and the j unordered.

I want to create (j, i) with j ordered and i unordered ie.


6940, 22886
6940, 38277
6940, 43788

38277, 567
38277, 90023
38277, 6940

I've tried the dictionary route and it works perfectly for small set of co-ordinate pairs but not for large sets as it hits memory capacity.

Any ideas how I could do this?

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