Now I'll say what is Sparse Table and I'll show you some problems that I found.
Sparse Table is a data structure, that allows answering range queries. It can answer range minimum queries (or equivalent range maximum queries) in O(1) time, and another queries in O(log n).
872B - Maximum of Maximums of Minimums //difficulty 1200 but with sparse table harder
5C - Longest Regular Bracket Sequence //difficulty 1900
475D - CGCDSSQ //difficulty 2000
863E - Turn Off The TV //difficulty 2000
514D - R2D2 and Droid Army //difficulty 2100
675E - Trains and Statistic //difficulty 2500
15D - Map //difficulty 2500
873E - Awards For Contestants //difficulty 2500
713D - Animals and Puzzle //difficulty 2700
SPOJ — RMQSQ //easy
Everything you can solve by sparse table.