I have written a blog post on how to solve Facebook Hacker Cup Round 1 problem Autocomplete using a trie. This is a beginner level article and is meant for those who want to know what a trie is and how to use it in programming problems.
Here's the link: http://blog.anirudhrb.com/2015/02/introduction-to-tries-through-facebook.html
Enjoy!
PS: If you are not a beginner, please navigate away from this page immediately and DON'T CLICK ON DOWNVOTE! :P