You forgot a couple important parts of the algorithm:

open the second input file
while reading the second input one line at a time
   if the current line exists as a hash key and the hash value is "1"
     print this line to the "matching lines" file
     increment the hash value  <--  YOU FORGOT THIS STEP


YOU STILL NEED TO DO THIS PART:

having read all input, now loop over all the keys of the hash
   if the hash value assigned to this key is still "1"
     print this hash key to the "distinct lines" file (maybe include t
+he file name)
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