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Solutions to weekly challenge 72 by Bob Lied.
https://perlweeklychallenge.org/blog/perl-weekly-challenge-072/
This week, I would like to add two personal elements to the problem:
(1) create a template for perl-vim that sets up these weekly challenges
(includes Test::More, a skeleton for checking ARGV, and whatever else
is quickly becoming a pattern; and (2) use a github issue in the submission
process, just to learn more about using git and github.
* TASK #1 > Trailing Zeroes
** Initial thoughts
Too easy, unless I'm missing something. The result gets a zero on the end every time
it's multiplied by 10, and since we're doing factorials, that will happen every time N
rolls past a multiple of 5. The answer is int(N/5), I think, but I'll need to convince
myself completely.
We could make it a little tougher by actually calculating N!, and maybe using Memoize
as an optimization. And maybe finding out how high N can be until overflow or waiting time
make it impractical.
** Post Solution Thoughts
Yep, it was really that easy. I implemented the factorial using Memoize just
for fun. The highest number that didn't roll over to floating point was 20!.
** Problem Statement
You are given a positive integer $N (<= 10).
Write a script to print number of trailing zeroes in $N!.
* TASK #2 > Lines Range
** Initial Thoughts
This has come up often enough that I know I've done it in sed and awk; and in
a pipeline with head and tail. The flip-flop operator comes to mind, but
there'll be some experimentation for boundary conditions. Also some test
cases for A or B being outside the range of the file or having an empty file.
** Post Solution Thoughts
The hardest part of this turned out to be how to set up tests. I wanted the
testing to be self-contained, so I put the test data into __DATA__. But then
re-reading that repeatedly for different tests required seeking back to the
start and also resetting $. A couple of trips to Google there.
I also wanted to capture the output in a variable and not just print to the
console. I knew that a string could be opened as a file handle using a
reference to the string. It should have been easy; but I spent a long time
debugging before I realized that I had typed \&TestResult instead of
\$TestResult.
** Problem Statement
You are given a text file name $file and range $A - $B where $A <= $B.
Write a script to display lines range $A and $B in the given file.
(That's A and B inclusive, from the examples.)
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