# [Community Puzzle] Format string validation

Coding Games and Programming Challenges to Code Better

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Iâve been lost on this for a bit. Maybe Iâm taking the wrong approach?

Iâm coding in JS, and Iâve had a few different logics Iâve tried out, and it end in one of two ways -
-The code becomes too complex to follow, so I paste my code into a notepad just in case, and start over.
-Limited by the approach

All of my logic seems to start the same. Divide the âformatâ by â~â, and use String manipulation to find the portions of it within âtextâ. This typically works to start, and has been my initial approach.

My first logic worked for every test except the last. I think I know why.
In a situation where the text is ZZABXDABCDFFABYDZZ, and the format ~AB?D?F~
I was working through it, dividing it out by the "?"s after dividing it out by "~"s, and although itâd find an instance of âAB?â in the string, it didnât find the right one, and I hadnât programmed a way for it to backtrack and try the next.

My most recent logic was to separate into two parts. Firstly, the beginning and the end. Thinking if I could separate the special case of if it starts with â~â or not, from the rest of the logic, it might be easier.

Iâm thinking maybe the answer lies somewhere in recursion? When learning programming, recursion is a topic thatâs always given me trouble. I usually am able to understand enough to pass the courses, but never enough to apply it in actual programming. I feel like itâs a valuable tool, but I struggle when applying it.

TL;DR â
I would like help.
Hints, or tips for the puzzle, or learning recursion in a way that I can see how to apply it?
Javascript-specific resources would be nice on the recursion, but Iâm also fine just learning the general logic of it.

Most of the published Python solutions I can see use either regex or recursion, so recursion is definitely a way to go. There are also solutions using dynamic programming and other approaches, but they are very few.

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If youâre not ready for recursion, you can solve this puzzle without it.

• First, write an âequalsâ function, to accept the â?â character (so that âABCDâ and âAB?Dâ would return true).
• Then, write a âfindâ function, using your âequalsâ function (so that it would find âAB?Dâ in âZZABCDZZâ), returning the index.

With those tools, you can just separate words by â~â as you said, and find each word in the text. Be careful about starting each search at the end of the previous one (thatâs why âfindâ returns an index. You start your search at the previous index + previous word.length(), so that âAB~BCâ wouldnât match in âABCâ).

And if itâs too easy with that âŠ you can try recursion.

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Iâm always sad when I hear this because recursion is supposed to feel a lot more ânaturalâ than programming with loops, so if a teacher makes loops easier than recursion they are doing something wrong in my opinion.

One way to think of recursion is that you have a trusted assistant who already knows how to do the task; you have to make just a little bit of progress yourself, but you can pass most of the task, as a subtask, to your assistant who already knows how to do it.

For instance, imagine you have to match ABXDABCDFF against ~AB?D?F~.

The very first thing to do is decide whether to include the first A into the ~ or not.

If you include it, then youâre left with matching BXDABCDFF against ~AB?D?F~, which you pass to your assistant.

If you donât include it, then youâre left with matching ABXDABCDFF against AB?D?F~, which you pass to your assistant.

So this gives us the following recurrence relation:

match(â~AB?D?F~â, âABXDABCDFFâ) =

Now this is a recurrence relation, you can

• use it directly to write a recursive function
• use it to fill a dynamic programming table where M[i,j] stores the result of match(substring starting at index i, substring starting at index j)
• use it for a stack-based or queue-based approach where you store all the pairs (format,text) that you want to try to match
• or anything else of your choosing.

(Also note I arbitrarily decided to do remove characters from left to right, but you can also do it from right to left if you prefer, ie remove the F before the A)

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ty all for the tips ~
Iâm going to try again later today.

Iâd really like to do it using recursion, so Iâm going to try that first.
Iâll comment again once I triumphantly complete the puzzle >:^)

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Thank you very much for this puzzle, I really enjoyed it.
It reminded me some lessons I had long time ago.

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I DID IT!!! WITH RECURSION!!! (kinda)
I donât know if it still counts as recursion, because I called the recursive function inside of a loop, but it works

Best part is, would have worked on my first try, but I forgot to pass the previous value of a variable when taking a step back, so it was statically set to false instead of taking a step back and using the previous value.

TL;DR thx for everyone that helped :):):).

Edit:

Iâm now realizing how much simpler this problem would have been to solve with regex xD

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Bonjour, je ne comprends pas pourquoi le test 8 est considĂ©rĂ© comme bon.

DĂ©but du texte = IboJSRam>|6&V17T_M|pw`w)m,<ns8{%9G5%%WT"S=f}k`ztLQ^eP-T/P-u@?LgbWjnmE
DĂ©but format . = Ibo~ . . . . >|6&~ . . . . . .pw~ )m~ . . . .{~ . . . . . . . . . . . . . . . . . . . -u@?LgbWjnm?/JB<
Ă§a coince ici. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .^

puisque aprĂšs le tiret (-) le format montre un âuâ alors que le texte donne un âTâ

Que nâai-je pas compris dans les consignes ? Merci de mâĂ©clairer.

Hello, I donât understand why test 8 is considered good.

Start of text . .= IboJSRam>|6&V17T_M|pww)m,<ns8{%9G5%WT â S=f}kztLQ^eP-T/P-u@?LgbWjnmE
Start format . = Ibo~ . . . . >|6&~ . . . . . .pw~ )m~ . . . {~ . . . . . . . . . . . . . . . . . . . .-u@?LgbWjnm?/JB<
itâs sticking here. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .^

since after the hyphen (-) the format shows a âuâ whereas the text shows a âTâ.

What did I not understand in the instructions? Thanks for clarifying.

Youâre saying

``````Text:   { %9G5%%WT"S=f}k`ztLQ^eP -T/P -u@?LGbWjnmE/JB<c
~~~~~~~~~~~~~~~~~~~~~~  not matched from here
Format: { ~                      -u@?LGbWjnm?/JB<c
``````

But you can also match the format this way:

``````Text:   { %9G5%%WT"S=f}k`ztLQ^eP -T/P -u@?LGbWjnmE/JB<c
~~~~~~~~~~~~~~~~~~~~~~ ~~~~
Format: { ~                           -u@?LGbWjnm?/JB<c
``````

does someone know what is in test Big case, I passed all the tests except the one after submitting the code, I would like to know what is in this test.

In Validator 8 (Big case), the input text is the same as that of Test 8, while the input format is around 50% the same as that of Test 8.

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you fail probably because ~?

Câest notamment le cas pour le problĂšme âWARâ, la bataille navale, pour lequel jâai vu passer une multitude de demande dâaide concernant le ramassage des cartes.

Ceci dit, jâaurais dĂ» me douter quâil fallait comprendre les consignes diffĂ©remment puisque des participants de "format string validationâ avaient rĂ©solu ce problĂšme. Je rĂ©flĂ©chirai plus longtemps la prochaine fois

Thanks for the clarification.

Some of the instructions could be improved.

This is particularly the case for the âWARâ problem, the naval battle, for which Iâve seen a multitude of requests for help in collecting the cards.

Having said that, I should have known that the instructions needed to be understood differently, as participants in âformat string validationâ had solved this problem. Iâll think longer next time

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