Find duplicate word in any string

Question

How would I be able to detect a duplicate word in any string given. example 'isonetoismany', detect the duplicate "is" and return true for finding a duplicate and false if none.

Answer 1

option 1.
have a list of words, test if one of them appear twice or more in the text.
option 2.
go from left to right.
a word is at least 2 chars, so cut 2 chars [0:1] and test if you find them again in the string, then [1,2]... and so on, until [len-2:len-1].
then with 3 chars and so on.

Answer 2

I saw below a challenge where you have to find a triplicated word. If you search it you can maybe find what you are searching.
Edit:
https://www.sololearn.com/discuss/1006164/?ref=app