Good API video watching and notes taken

Oct. 22, 2015

  Spent time to look into the note through the video, and then study more later:

How To Design A Good API and Why it Matters (Julia's rating: A+)
https://www.youtube.com/watch?v=aAb7hSCtvGw


1. Watched again on 10/21/2015, notes taken to share:
54:40/1:00:18
Use Appropriate Parameter and Return Types
. Favor interface types over classes for input
- provides flexibility, performance
. Use most specific possible input parameter type
- Moves error from runtime to compile time (Julia's comment: Great tip, reduce time on debugging, fix things in compiling time!)
. Don't use string if a better type exists
- Strings are cumbersome, error-prone, and slow
. Don't use floating point for monetary values
- Binary floating point causes inexact results!
- Use double (64 bits) rather than float (32bits)
-Precision loss is real, performance loss negligible

2. watched again on 10/21/2015, notes taken to share:
49:19/1:00:18
Don't violate the Principle of Least Astonishment

Read more on this article:
http://programmers.stackexchange.com/questions/187457/what-is-the-principle-of-least-astonishment

3. watched again on 10/21/2015, notes taken to share:

42:31/1:00:18

Subclass only where it Makes Sense

. Subclassing implies substitutability (Liskov)

-- Subclass only when is-a relationship exists

-- Otherwise, use composition 

. Public classes should not subclass other public classes for ease of implementation

Bad: Properties extends Hashtable 

        Stack extends Vector 

Good: Set extends Collection 

Cache design, dynamic programming - matrix region sum

June 25, 2015

Introduction

It is my firs time to read the algorithm and I am so surprised to learn the algorithm. I love the learning and also very happy to read the blog with good and very clear explanation of the algorithm.

Problem statement:

Given the integer matrix, top left and bottom right coordinates of the rectangular region, calculate the region sum.

Here is one of blogs I like to read and share. 

Make it more time efficient

Naive solution, O(n x m) calculation of addition to get the sum. How to get it as O(1) using cache, how big the cache space?

Naive way to design the cache, it takes O( n² x m²) space. The efficient way is O(n x m), using dynamic programming.

Share the practice C# code, here is the link.