Hi, everybody.

The question is :

if the user input a set of numbers, you don't know how long the

set is, like 1, 2, 3, 4, 5, 5, 5, 6, 1, 3, -1, -12141, 123, -1...., you are

asked to find the dumplicate numbers in this set. I mean 1, 5, -1.

Acturally, I just can find an o(n ^ 2) algorithm by scaning the

set for n times.

I think there must be a better way, maybe O(n) or less:)

Just for fun:)