A simple data structure that supports fast range queries in an array. However, it is usually only valid for reversible operations, like addition and subtraction
Binary Indexed Tree is represented as an array. Each node of Binary Indexed Tree
stores sum of some elements of given array. Size of Binary Indexed Tree is equal
to n where n is size of input array. In current implementation we have used
size as n+1 for ease of implementation. All the indexes are 1-based.
