Returns the rank of each element with each column of a matrix. So, if row 34 is the highest number for column 3, then the first row of column 3 will be 34 -- unless it is column 34, in which case it will be 35, to adjust for the fact that this is a single-sided market.
sortIndexOneSided(u)
A matrix with agents' cardinal preferences. Column i is agent i's preferences.
a matrix with the agents' ordinal preferences