Problem 42386. Faint Receipt

Created by goc3

Solve Later

Suppose you have a receipt with some numbers that have been smudged or didn't print. In particular, the total amount is missing the first and last digits. The purchase did not involve tax (or you're looking at the subtotal before tax), only one item was purchased, and the quantity of the item is known. Use this data to determine what the total amount was, assuming that the unit cost does not contain a fraction of a cent. The partially known total will be provided as a string with an X for the unknown first and last digits.

In some cases, there will be multiple possible answers. We're going to assume the best and return the lowest possible total. The second missing digit can range from 0 to 9, though the first missing digit is the leading number, and, therefore, cannot be zero.

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38 Solutions
11 Solvers

Last Solution submitted on Nov 19, 2018

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7 Comments

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Alfonso Nieto-Castanon on 17 Jun 2015

there may be a few incorrect tests here (e.g. test 2 with 'X31.6X' and qty=111 should return '531.69' if I am interpreting correctly)

bainhome on 17 Jun 2015

agree with alfonso

James on 17 Jun 2015

I had the same issue with that particular test case.

goc3 on 17 Jun 2015

I've updated the test suite. It should work now. I selected the option to have all previous solutions rescored, but I've never actually seen that option work for other problems I've worked on, so just submit your solutions again. Also, refer to comments on http://www.mathworks.com/matlabcentral/cody/problems/42385-combined-ages-4-non-symmetric-with-multiples-n-3 regarding not being able to use the "Test reference solution" button currently. Is anyone else having that problem?

Jan Orwat on 17 Jun 2015

I believe rescoring doesn't work immediately, but all solutions seem to be rescored now. "Test reference solution" doesn't work for me neither. As far as I remember it's not the first time it doesn't work (on my account), but previous incidents had shorter duration (week or so).

Jan Orwat on 17 Jun 2015

http://www.mathworks.com/matlabcentral/cody/solutions/686845#comment_5568

goc3 on 17 Jun 2015

That link doesn't work as written (at least, it didn't for me). It does function, though, if you truncate the url at #.

Solution Comments

Solution 688374

1 Comment

1 Comment

Alfonso Nieto-Castanon on 18 Jun 2015

Funny behavior of possible over-reactive spam filter in Cody: changing this code to use instead of char(str2num('[49 36 49.... 36 50 57')) the actual char array '1$1...$29' will get you an "inappropriate content" flag... I admit no regexprep string should ever have that many dollar signs...

Solution 688327

5 Comments

5 Comments

Show 2 older comments

Jan Orwat on 17 Jun 2015

fails for partial_amt = 'X67.9X'; qty = 9; and many, many others

goc3 on 17 Jun 2015

A bunch of your solutions now pass the test suite, so perhaps this comment is outdated?

Jan Orwat on 18 Jun 2015

In above case it returns 567.90, correct answer would be 167.94. This solution is minimizing last digit which works in most cases, but is based on wrong assumptions. It passes test, but doesn't solve the problem. Yes, my later submissions doesn't have this bug, but I'm unsatisfied when those wrong ones are going through the test alive :-)

goc3 on 18 Jun 2015

You had me confused, since that specific combination isn't in the test suite, but I think I understand now. In your quest for perfection, you've been testing the solution against more test cases. That's the really difficult thing about making these problems—coming up with a robust test suite that's in-depth enough to only let completely correct solutions through.

Jan Orwat on 19 Jun 2015

Sorry Grant. Yes, I'm used to do more tests and I was suspicious about my algorithm.

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Problem 42386. Faint Receipt

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