Ten days of statistics (2) - Quatiles, Standard Deviation
Let's learn basic statistics in 10 days -
Ten days of statistics (1) - Mean, Median, Mode
Let's learn basic statistics in 10 days 
Binary Indexed Tree (Fenwick Tree)
A Fenwick tree or binary indexed tree (BIT) is a data structure that can efficiently update elements and calculate prefix sums in a table of numbers 
Collection of bit mask operation
I have collected a few popular and useful bit operations 
Modular Inverse
In arithmetic, a modular multiplicative inverse of an integer a is an integer x such that the product a*x = 1 with respect to the modulus m