day4-2.prdc

iIg~M…Sm$pf{GLm2#}ç .. 19 bytes

{
iIg~M…Sm$pf .. as in day 1, produce a list of sorted strings of numbers
{  .. count how many numbers satisfy this predicate:
  G  .. group
  Lm .. map by taking the length
  2# .. find occurrences of 2
}ç .. count by the above block
};