David Eppstein's code is very nice.
Here's the python version of the perl code:
�# -*- coding: utf-8 -*-
�# Python
�
�def combo (n):
� '''returns all possible (unordered) pairs out of n numbers 1 to
n.
�
� Returns a dictionary. The keys are of the form "n,m",
� and their values are tuples. e.g. combo(4) returns
� {'3,4': (3, 4), '1,4': (1, 4), '1,2': (1, 2),
� '1,3': (1, 3), '2,4': (2, 4), '2,3': (2, 3)}'''
� result={}
� for j in range(1,n):
� for i in range(1,n+1):
� m = ((i+j)-1) % n + 1
� if (i < m):
� result["%d,%d"%(i,m)]=(i,m)
� return result
�
�print combo(4)
So sweet.
Xah
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