Menu
Questions similar to this have been asked before on SO, but they're not quite what I need and I can't seem to arrive at my solution through altering/modifying those approaches.
In any case, I have an array of arrays, as follows:
b= [["1"],["2"],["3"],["4"],["5"],["6"]]
(If it makes it easier to arrive at a solution, b can also be a one dimensional array, as follows: ["1","2","3","4","5","6"]. Either type of input works for my needs.)
and I would like to generate the following:
[["123456"],["213456"],["312456"],...]
where each array in the output array is a unique permutation of the six numbers. I would also take it as a single array (e.g., ["123456", "213456",...]). The order of the output isn't particularly important as long as each entry is unique and no number repeats in a string (e.g., "112345" isn't allowed). All 6 numbers must also be used in each entry, so I'm not interested in incremental output like "123", either.
As much as this sounds like it, this isn't a homework problem. I could brute for this thing and get the output I need. I just feel like there has to be a better, more elegant, solution.
625
An array is a data structure that represents a list of values, called elements. Arrays let you store multiple values in a single variable. In Ruby, arrays can contain any data type, including numbers, strings, and other Ruby objects. This can condense and organize your code, making it more readable and maintainable.
Ruby arrays are ordered, integer-indexed collections of any object. Each element in an array is associated with and referred to by an index. Array indexing starts at 0, as in C or Java.
Ruby printing array contentsThe array as a parameter to the puts or print method is the simplest way to print the contents of the array. Each element is printed on a separate line. Using the inspect method, the output is more readable. The line prints the string representation of the array to the terminal.
With Array#permutation:
permutations = (1..6).to_a.permutation.map(&:join)
# ["123456", "123465", "123546", ..., "654312", "654321"]
Ruby does this natively :) From the ruby documentation :
a = [1, 2, 3]
a.permutation.to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
a.permutation(1).to_a #=> [[1],[2],[3]]
a.permutation(2).to_a #=> [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]]
a.permutation(3).to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
a.permutation(0).to_a #=> [[]] # one permutation of length 0
a.permutation(4).to_a #=> [] # no permutations of length 4
http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-permutation
20
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
