To find if any permutation of pattern exists in the text.
To find 11th 11-digit prime in the digits of PI
http://www.hackerearth.com/india-hacks-2014/algorithm/gotta-catch-em-all/
HackerEarth: IndiaHacks 2014 problem Reverse Primes
HackerEarth: IndiaHacks 2014 problem Once upon a time in Time-Land