1.Stack->
1.create a stack using array 2.Delete Middle Element from Stack 3.Valid Parenthesis 4.Insert an element at bottom of stack 5.Sort a stack using Recursion 6.Redundant Brackets 7.Min cost to convert a string 8.Next Smaller Element 9.Previous Smaller ELement 10.Largest Rectangle Area in Histogram 11.The Celebrity Problem 12.MaxAreaRectangle in BinaryMatrix