When to buy and sell stock
http://leetcode.com/2010/11/best-time-to-buy-and-sell-stock.html
Rotated binary search
http://leetcode.com/2010/04/searching-element-in-rotated-array.html
trie c implementation
http://www.geeksforgeeks.org/trie-insert-and-search/
No need to add length to c array