What's the missing column/row? (GCJ 2016-1A rankfile)
CJam, 5 - 10% = 4.5

This is an unnamed function (block) that takes an array of arrays and returns an array:

{:^$}


(With some inspiration from Dennis)

Try it online

And here is the code I actually submitted at GCJ (24 bytes):

li2*({l~}*]$e`{(2%*~}%S*


Try it online

Explanation:

This basically lists the values that appear an odd number of times.

:^    reduce by symmetric difference; pairs of duplicate values "cancel" each other
$     sort the resulting array