Problem 42404. Divisible by 2

Created by goc3

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This is the first problem in a set of "divisible by x" problems. You will be provided a number as a string and the function you write must return whether or not that number is divisible by x.Rather than allowing you to use an easy way out, such as the modulus function, division and checking the result against its rounded value, Java functions, etc., you get to learn and apply integer divisibility rules. For reference, some divisibility conditions for integers are listed <a href = "http://en.wikipedia.org/wiki/Divisibility_rule">here</a>. Other such references are also available elsewhere on the internet.There are two benefits to approaching divisibility in this manner: first, you learn neat divisibility tricks that you can use in your head or on paper for large numbers and, second, you program a routine capable of determining divisibility for arbitrarily large numbers, for which existing precision fails. So, to begin...Write a function to determine if a number is divisible by 2. This will be the case if its last digit is even.(This problem blocks a range of functions in the first test case so that you must use one of the supplied methods; some of these restrictions will be lifted for later problems in the series.)Next problem: <a href = "http://www.mathworks.com/matlabcentral/cody/problems/42405-divisible-by-3">divisible by 3</a>.

This is the first problem in a set of "divisible by x" problems. You will be provided a number as a string and the function you write must return whether or not that number is divisible by x.

Rather than allowing you to use an easy way out, such as the modulus function, division and checking the result against its rounded value, Java functions, etc., you get to learn and apply integer divisibility rules. For reference, some divisibility conditions for integers are listed <http://en.wikipedia.org/wiki/Divisibility_rule here>. Other such references are also available elsewhere on the internet.

There are two benefits to approaching divisibility in this manner: first, you learn neat divisibility tricks that you can use in your head or on paper for large numbers and, second, you program a routine capable of determining divisibility for arbitrarily large numbers, for which existing precision fails. *_So, to begin..._*

Write a function to determine if a number is divisible by 2. This will be the case if its last digit is even.

(This problem blocks a range of functions in the first test case so that you must use one of the supplied methods; some of these restrictions will be lifted for later problems in the series.)

Next problem: <http://www.mathworks.com/matlabcentral/cody/problems/42405-divisible-by-3 divisible by 3>.

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Last Solution submitted on Sep 19, 2021

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8 Comments

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bainhome on 25 Jun 2015

how about function "rem"?

goc3 on 25 Jun 2015

Thanks for the catch. I've added that function to the outlawed list for this and all subsequent problems in this set. Let me know if there are any other functions that should be added to that list.

David Verrelli on 15 Apr 2017

FYI, I had commented my code with text that included the word "remains". This triggered a false positive in the test for forbidden function "rem". Perhaps it is possible to forbid instead "rem[spaces]("?

David Verrelli on 15 Apr 2017

I suggest that "factor" should be (or should have been) banned.

goc3 on 19 Apr 2017

I added factor to the banned list. [Though, the test suite includes very large numbers (as strings) that are beyond the storage limit of single- or double-precision variables.]
Also, that sort of string with wildcards (for capturing rem) would work if regexp were used, but I use strfind in the test suite. That way, only the direct use of those exact strings will trigger that test case to fail.

Donovan Greene on 15 Jun 2017

Many solutions can be made that only check 0, 2, and 6 and fail on 4 and 8, thus not checking properly. The tests should include more unique ending digits, at least one of each 0-9.

Donovan Greene on 15 Jun 2017

Your test cases only ever end in 0, 1, 2, 3, 6, and 7 and many solutions give the wrong answer on 4, 5, 8, or 9.

Maryam HCTRAK Yousef on 14 Aug 2020

It shows me wrong.

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