I have an array of 1000 numbers, randomly generated. 10 of those numbers must be between 0-9 (including 0 and 9), and 10 of those numbers must be between 991 and 1000 (including 991 and 1000). This is what I came up with:
arr = []
980.times do
arr << (11..989).to_a.sample
end
arr2 = []
10.times do
arr2 << rand(10)
end
arr3 = []
10.times do
arr3 << (990..1000).to_a.sample
end
arr4 = []
arr4 = arr + arr2 + arr3
arr4.shuffle
Is there a more elegant way to do this in ruby?
Some notes:
Try to learn some functional programming, you shouldn't write Ruby as it were a low-level language (like C). Favor expressions over statements. My 2-cents on the matter, I hope it helps: http://www.slideshare.net/tokland/functional-programming-with-ruby-9975242
Let me show a simple example of using FP. The first 4 lines of your code could be written like this: arr = 980.times.map { (11..989).to_a.sample }
arr4 = []: Why? the next line assigns it to another expression.
range.to_a.sample. That's very inefficient, better rand(range).
I'd write:
ranges = [0..9, 11..989, 990..1000]
output = ranges.flat_map do |range|
range.map { rand(range) }
end.shuffle
ranges.reduce([]) {|arr, range| arr + Array.new(range.size) {rand(range)}}.shuffle
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Commented
Jan 8, 2014 at 7:54
reduce with + leads to O(n^2) code.
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Be careful at the boundaries — you didn't implement what you wanted. The output will never contain 10, and it might include 990 among the [991, 1000] range.
