This is an entry for the 16th Fortnightly Challenge.
Jim : Bob, I have solved the puzzle !!
Bob : I do not believe you, show me !
Jim : No, you have to solve it yourself.
After some discussion between them how Jim can prove that he has solved the puzzle without showing Bob the answer. Jim cuts his answering paper into pieces, then Jim shows a set of numbers.
Jim : look these numbers, they are all unique right ?
Jim does that more than 20 times
What puzzle had Jim solved ?