Moments on Perl or other Programming Issues

PWC#068

Inexperienced in object-oriented, (after a few hours violent trial and error, ) I finally gave up the task #2 reordering a singly linked list.

For the task #1 zero matrix (task statement here), I handled it innocently. By the way, I read the review by Mr Crain and deeply recommend others read Myoungjin Jeon's solution.

PWC#069

Task #1 - Strobogrammatic Number

I use the combinatorics library on CPAN. However, a poorly designed code performs poorly in the face of combinatorial explosion, in comparison with other PWC members' scripts. If I had considered symmetry, as the Perl Reviewer Mr Crain stated, the code would be more effective.

There is a mistake on my code: I treat all single digits as strobogrammatic. Forgetting what happened around during that week...

After finishing my codes, usually I will look on others' blogposts and see if there are any gems of Perl idioms, optimization or algorithms. (For the first of these three things, usually I cannot understand; still a novice! Learning Perl or Beginning Perl is consulted, in particular of anything with references.)

Task #2 - 0/1 String

Before the update (asking for S₃₀, instead of S₁₀₀₀), I thought it had been a task challenging BIG integers or LONG strings handling... .

Back to the task. I have "jumped a step" by generating S_N from S_N-2 instead of S_N-1. For the S₃₀, I forcefully generated it from S₂₆, which is the largest S _i can be properly generated by the core of my code (and computer memory).

PWC#070

Task #1 - Character Swapping

Got familiarity with substr.

Task #2 - Gray Code Sequence

I learnt about Gray code in my first semester in university, in a combinatorics class I did poorly. (I did poorly in every class that semester, including linear algebra and multivariable calculus.) Anyway, the Gray code looks easier now.

Bravely (Boldly?), as a novice in programming, I submitted a script in Lisp! I haven't got time to study Perl Best Practices but I have jumped to learn a new language... while I haven't figured out or got resources on best practices of Lisp.

PWC#071

Task #1 - Peak Element

I must warn myself to read instructions and examples carefully. I:

1. missed the two edge cases;
2. generated 11 elements instead of 10 elements;
3. had almostly missed the uniqueness requirement for the elements, but after causally reading laurent_r's blog in the morning(GMT+8), I rushed to add a few lines;
   
4. thought it had been fixed it up? But I forgot to declare a hash, so the submitted code was actually refused to run under use strict.

I wrote a Lisp script for this task. Lots of setf was used, after 10 days, I think the code will be more readable and maintainable using some defun.

Task #2 - Trim Linked List

Singly linked list again! OO. OO. OO. Is it necessary to make a class of nodes and linked list? I "consulted" Rosetta Code and learnt to implement linked lists by nested hashes.

PWC#072

Task #1 - Trailing Zeroes

Most members output a complete and grammarically correct English sentence, as in the example. Again, I forgot the formatting.

For personal record: I wrote a Lisp script for PWC tasks again.

Task #2 - Lines Range

Just digged out the Learning Perl.

Sidenote

I have gradually developed a format for my submissions.

Firstly, put the task statement with the habitual or necessary heading statements (

#!/usr/...
task statement
Usage: ch-x [parameters]
use strict;
use warnings;).

Secondly, I put the example test case as default values and allow people deal with my codes from command-line arguments. (

if ($ARGV[0] and $ARGV[1]) { $S = shift @ARGV; @A = @ARGV; } else { $S = 3; @A = (1, 5, 0, 2, 9, 3, 7, 6, 4, 8); } )

This may help when I try to look for or review my codes written.

PWC#073 (submission deadline: the coming Monday GMT+8 0759)

"Write test cases first!" I would try to follow this "software engineering" rule of thumb^## (especially for scripting language?).

Task #1 - Min Sliding Window

I have learnt to use is_deeply this time.

Just thinking the optimization if we know the minimum values are rare and both $S and the list are large. See if I can write a script suitable for the above condition and show its complexity^# within this weekend.

Task #2 - Smallest Neighbour

No need to be very observant, we can see there are some patterns of the output like [0 , min₁ ,0 , min₂, min₂, 0, min₃, 0 , min₄, ..., 0, min_last ] where min_i > min_j for i < j. In words: a weakly descending sequence with some zeroes interpolated.

Time to learn Lisp and see if I have time and knowledge to write a Lisp script as part of guest submissions for PWC.

(Again...) Wish you all stay healthy mentally and physically! □

My codes can be found on the E7-87-83 GitHub repository. You may appreciate others' codes on the official GitHub repository Knowledge base of PWC.

Do tell me , if you have oppositions!

#: I am very lazy on writing proofs. However, I took all required courses in math (not all with flying colours) in university but forgot to declare double major in Physics and Math, thus I graduated with a BSc in Physics only. Sometimes I would have resentments towards this life episode; sometimes I comfort myself by telling that I am neither good at writing rigorous proofs nor linear algebra computations, thus the certificate might avoid some embarrassment.

##: See Testing Is the Engineering Rigor of Software Development, by Neal Ford, in 97 Things Every Programmer Should Know. I think I read the importance of (unit) testing elsewhere also.

 Addendum (on 16th Aug):

(here >> means "much greater than")

input: approx 15900 integers
S=20

ch-1.pl
real	0m0.069s
user	0m0.049s
sys	0m0.020s


ch-1a.pl
real	0m0.064s
user	0m0.044s
sys	0m0.019s

S=30

ch-1.pl
real	0m0.075s
user	0m0.062s
sys	0m0.013s

ch-1a.pl
real	0m0.066s
user	0m0.053s
sys	 0m0.012s


S=100

ch-1.pl
real	0m0.078s
user	0m0.064s
sys	0m0.014s

ch-1a.pl
real	0m0.052s
user	0m0.031s
sys	0m0.015s