If that was the case I think b/c I did Regex.Split(@"\s+"), which is unneccessary since white space is just a char other than ,.<>.
I regret so much.. Thanks for letting me know! ;)

Where can we see the execution time?

1. In the original problem, it calls Decrypt multiple times.
2. For 3, if you filter with Regex, you don't need to do search.