TASK #1 › Pattern Match
Task
You are given a string $S and a pattern $P.
Write a script to check if given pattern validate the entire string. Print 1 if pass otherwise 0.
The patterns can also have the following characters:
- ? - Match any single character.
- * - Match any sequence of characters.
My solution
This seems pretty straight forward. I take the pattern, escape the meta characters, except ? and *, replace the ? with . and * with .+, anchor the regexp to the entire string, and then test the match.
The only question is does 'any sequence of characters' include a sequence of 0 characters? I assumed it doesn't, but if it did, replace .+ with .*.
Examples
» ./ch-1.pl abcde "a*e"
1
» ./ch-1.pl abcde "a*d"
0
» ./ch-1.pl abcde "?b*d"
0
» ./ch-1.pl abcde "a*c?e"
1
TASK #2 › Unique Subsequence
Task
You are given two strings $S and $T.
Write a script to find out count of different unique subsequences matching $T without changing the position of characters.
My solution
For this task I used a recursive subroutine called _find_string. It starts with the two input vales, and works through each character in $S until the first character is found. When this occurs, I call the function again with $S now the remainder of the string, and the first character of $T removed. Once we get to the end ($T is the last character) we add 1 to the $matches variable.
I'm not sure a recursive function is the best way to complete the task, but it works. If performance was an issue, we could always reduce $S to only contain the characters in $T, something like: $S =~ s/[^$T]//g; and escaping the meta characters as needed.
Examples
» ./ch-2.pl littleit lit
5
» ./ch-2.pl london lon
3
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