Sudoku Checker

Sudoku Checker

Problem Statement

Given  a vector<vector<int>> of size 9*9. Check whether it is a valid Sudoku or not.  

Problem Solving 

• I thought of starting with Iterators, writing Iterators for row iterator a column iterator and square iterator. 
• This got me involved in a lot of Object Oriented Problem and how to implement == nicely. 
• That got me stuck on the double dispatch problem and further after few frustrated days, I found a book, Effective C++. 
• Now after having read that book and coming to chapter 2. I thought I had one solution and I restructured the Object modeling and yes it did work.
• This whole thing took a lot of time. around 2 weeks now. 
• Then I peeked in the book and answer in the book seemed very short and concise.
• Hah.. I think I created a complex solution to a simpler problem. 
• The solution in the book is very clean, basically instead of iterators and their complex hierarchy and initialization on objects this solution has a function that takes in a row_start , row_end, col_start, col_end and the original matrix. 
• Instantly I can see how easy it would be, the signature of the function would reveal it's algorithm. 
• But okay. I think this was a good learning. 
• The solution would be iterate all rows cols and sub matrices and check if anyone has duplicates. 
• checking for duplicates can be done via a set or bit vector. 

 Learning

• Multiple learning here. 
• First I think I should fork my problem solving skill from OO modelling skills. 
• So I have picked up a new book Programming Pearls. 
• All other learning were related to c++ and it's OO nature. 
• This took a lot of time and broke the rhythm. 
• I still do not know when is the time to give up and look in the book.