March 18, 2016
Problem statement is here.
Introduction
Julia likes to try a new way to train herself to expand
C#, C++ , Java, and JavaScript languages, by reading the solutions first, followed up
with a study to feed curiosity, make learning more fun.
Read other people's code! It may be big surprise. Julia is out-of-date to catch up C# skills, when she read those lamba function and LINQ code, she was shocked how concise it is.
Writing this blog is to help herself to advance her skills in language C#, the more she writes about her learning process, the more she involves with the community, she gets much smart every day. You do not believe it? -:)
Julia's C# implementation is here.
Thinking in all languages
Let us go over some submissions and then write down what
players do to solve the problem.
Julia reads 5 different languages at least 10 solution each, total more than 50 solutions. To learn C#, C++, Java, JavaScript, she likes to have
this extensive reading on algorithm code submissions, and then build up her daily routine
as a software programmer. Read code is most challenging and exciting work to build up a good programmer.
A list for each language in her arsenal:
C# - Read first, then write
C++ - Read more C++ code, prepare to write any time
Java - Read more
JavaScript - Julia tries to read more JavaScript code,
focus on reading for next 2 months
Thinking in C# 15+ ways
How to think about 15+ ways in C#? Enumerate the class
and API you like to solve the algorithm two strings. Are you ready for this?
She also likes the following C# solution by other
submissions:
Here is the link to go over all C# solution on two string
algorithm on Hackerrank.com, called two string C# solutions.
Do it yourself before code tour
Before you read the solution, can you think about using
C# Hashset, Dictionary, String.Contains, Hashset.Overlap method,
string.indexOf, Hashtable, string.Intersect etc. solve the problem?
Dictionary
Hashset
Hashset.Overlap
Hashtable
String
String.Contains
string.indexOf
string.Intersect
Using two pointer to solve the problem
Code tour
20 code submissions are listed to study. C# classes are used in the following orders:
Array
Dictionary
Enumerable
HashSet
HashTable
IEnumerable
String
StringBuilder
APIs are most important things to learn in coding.
1. Hashset
use hashset - more efficient, code is here.
read hashset constructor on Microsoft website. Excellent, Julia is learning to write new C# code
2. ToList
Read Enumerable.ToList<Source> method on Microsoft
site first. Link is here.
Read Enumerable.ToAny<Source> method on Micrsoft
site, link is here.
3. string.intersect API
Code submission is here to
study.
4. using C#, var, foreach, Any method
- interesting to read
5. IEnumerable - interesting to read
the code
Read IEnumberable: C++ analog - duck typing, a
question on stackoverflow.com. Link is here.
IEnumberable - Java analog
stackoverflow question is here.
6. Two
hashsets
7. Hashset - overlaps method - code is readable
Hashset overlap API
8. Array, Array.BinarySearch method - it is not time efficient
solution - but code is reusable.
9. Declare new struct data, use byte type,
and code is beautiful, succinct.
10. use two pointers, move forward if need separately - can be reused.
11. Two things Julia likes:
'z'-'a' in array declaration,
second one is to use one array int[26], not 2; second one
is char array
bool[] founded = new bool['z' - 'a' + 1];
char[] secondWord =
Console.ReadLine().ToCharArray();
12. Use Hashtable
13. Use string.Contains() method
14. Use Dictionary class
Dictionary<int, char>
Dictionary<int,char>
dex = new Dictionary<int,char>();
Dictionary
method ContainsValue()
15. string.ToCharArray(), Distinct() of
Char Array, ToList(), ToArray(), string.IndexOf methods
16. Use string.Contains, two dimension array
17. use Dictionary<char, bool>
18. use StringBuilder to concatenate output
Read the discussion StringBuilder vs string to
concatenation
a question on stackoverflow.com, the article is here to read.
One more article to read:
19. use " " to
concatenate two input strings and then .Split them
Code is here.
Last one, 20:
IEnumerable - Code is here.
StringBuilder
Read StringBuilder article on support.microsoft.com. Here is the article link.
Take some notes here:
1. the benefits of using the StringBuilder class over
traditional concatenation techniques
2. C/C++ strcat() - to allocate a large character array
as a buffer and copy string data into the buffer.
3. In .NET framework, a string is immutable; it cannot be
modified in place. <- immutable explanation!
4. The C# + concatenation operator builds a new string and causes reduced
performance when it concatenates large amounts of text.
5. .NET framework, a StringBuilder class is optimized for string
concatenation.
same as using a character array in C/C++, as well as automatically growing the
buffer size (if needed) and tracking the length for you.
6. Reuse existing StringBuilder class rather than reallocate each time you need
one. This limits the growth of the heap and reduces garbage collection.
StringBuilder makes more efficient use of the heap than using the +
operator.
Statistics
More than 3 hours to work on this study, thinking in C#.
Future master of C#
programmers
It is the big world since millions
programmers are working right now. How to advance the skills to compete?
The idea of training on hackerrank is simple, easy to access, and the resource is good since the code passes all test cases on hackerrank, and it is free.
The study of thinking in 15+ ways are a good start for Julia to master C# programming language. First Julia has to reach out to the community to see how other people think in C#, and then document the study, and then understand the thinking process in all the ways.
Julia likes to be the master of C# programming language, and also a good problem solver. Every idea counts.
Follow up
May 5, 2017
Spent more than 2 hours to clean up the blog, make it more readable, fix issues on styles like font color, size, layout, subheading etc.
Practice those C# solution.
Compare hackerrank code submissions study with other choices, such as taking courses or reading a book on C#.
