Regex not meeting the requirement

Question

I am trying to learn Regex construction, and i am stuck in one problem.

Problem Statement: A regex that should match following phrases:

rap them
tapeth
apth
wrap/try
sap tray
87ap9th
apothecary

but should not match

aleht
happy them
tarpth
Apt
peth
tarreth
ddapdg
apples
shape the

My attempt:

^[a-z0-9]+p.?t

My regex is matching tarpth as well. How can i fix it?

With your stated requirement: `^(?:rap them|tapeth|apth|wrap/try|sap tray|87ap9th|apothecary)$` — Lucas Trzesniewski, Jun 29 '15 at 12:46
@DenysSéguret This is sample problem i picked from http://regex.sketchengine.co.uk/cgi/ex2.cgi — Gaurav Gupta, Jun 29 '15 at 12:47
@LucasTrzesniewski Certainly this is the solution to the problem, but it looks like piping the keywords themselves should not be done. Reason for it is, it won't be having much logic embedded in it. But thanks for suggesting this way as well. — Gaurav Gupta, Jun 29 '15 at 12:51
I'm voting to close this question as off-topic because this is just a puzzle, not a real question — Denys Séguret, Jun 29 '15 at 12:52
@GauravGupta I was just pointing out that your problem statement is unclear, if you don't state the logic explicitly a bruteforce approach will do fine. — Lucas Trzesniewski, Jun 29 '15 at 13:06
@LucasTrzesniewski I got your point, Even brute force is a way to get solution. — Gaurav Gupta, Jun 29 '15 at 13:11

score 2 · Answer 1 · answered Jun 29 '15 at 12:51

2

This meets this requirement:

^([a-z0-9]+p.{1}|[a-su-z0-9]+p)t

Demo:

answered Jun 29 '15 at 12:51

n-dru

score 2 · Answer 2 · answered Jun 29 '15 at 12:51

2

This should do it - you failed to require a before the p:

.*ap.?t.*

answered Jun 29 '15 at 12:51

Armand

score 1 · Accepted Answer · answered Jun 29 '15 at 12:50

1

Looks like this regex does the trick, it's a very specific question thought:

(ap)(.?)t

answered Jun 29 '15 at 12:50

Carlo Moretti

3 Answers3