Some of my Hackerrank solutions
https://www.hackerrank.com/challenges/ctci-ransom-note
https://www.hackerrank.com/challenges/ctci-balanced-brackets
https://www.hackerrank.com/challenges/ctci-contacts
https://www.hackerrank.com/challenges/ctci-find-the-running-median
Code to check if all the characters in the string are Unique.