How to write a greedy algorithm for this problem?

I have a set X which in turn consists of n sets A_i. Each A_i is of different size and each A_i has a value attached to it. I want to partition X into k<n sets B_j where each partition consists of sets A_i which share the same value. k has to be less than n.

I want to use a greedy algorithm to do this but don't know how.

[Walter Roberson]

duplicates http://www.mathworks.co.uk/matlabcentral/answers/59242-how-to-write-a-greedy-algorithm-for-this-problem