CODEWITHSUNDEEP
rubyarraysrandomslice
Ryan Perera
Ryan Perera

Reputation: 115

Whats the best way to split an array in ruby into multiple smaller arrays of random size

I have multiple arrays in ruby of variable length from 1 to 40 :

@items is a typical array which could be anywhere from 1 to 40 in length. eg

@items = [1, 2, 3, 4, 5, 6]

I want to randomly split the array into smaller arrays of lengths either 1, 2 or 3 to give a result of (for example)

@items = [[1, 2],[3],[4,5,6]]

or

@items = [[1],[2, 3],[4],[5,6]]

etc

I know you can split the array using @items.each_slice(3)... where 3 is a fixed length. But i want to randomly split large arrays of variable length into array sizes of 1,2 or 3 randomly... Whats the best way to achieve this?

Upvotes: 4

Views: 905

Answers (5)

dbenhur
dbenhur

Reputation: 20398

Just for yucks, I thought I'd try a pure functional form with no mutating methods for this problem:

( ([email protected])
    .inject([0]) { |m,_| m + [m.last + 1 + rand(3)] }
    .take_while  { |i| i < @items.size } + [@items.size] ).
  each_cons(2).
  map { |s,e| @items[s...e] }

Upvotes: 1

philosodad
philosodad

Reputation: 1808

This solution maybe uses too many local variables, but it is non-destructive to the input array and flexible on array window maximum. 

def rotateAndTake inputArray, windowSize
  rotator, returnArray, breaker = 0, [], true
  while breaker do
    window = rand(windowSize)+1
    if(rotator + window > inputArray.length) then
      window = inputArray.length - rotator
      breaker = false
    end
    returnArray << inputArray.rotate(rotator).take(window) if window > 0
    rotator += window
  end
  returnArray
end

Also, I just wanted to write a solution that used the "rotate" method.

Upvotes: 1

Mladen Jablanović
Mladen Jablanović

Reputation: 44090

Here's another functional solution:

( [0]+
  (1..a.length-1)
    .to_a
    .sample(rand(a.length))
    .sort+
  [a.length]
).each_cons(2).map{|i,j| a[i..j-1]}

Upvotes: 0

sawa
sawa

Reputation: 168199

items, @items = @items.dup, []
@items.push(items.shift(rand(1..3))) until items.empty?

Upvotes: 7

oldergod
oldergod

Reputation: 15010

a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
b = []
until a.empty?
  b << a.shift((1..a.size).to_a.sample)
end
# b => [[1, 2], [3, 4, 5, 6, 7], [8, 9], [10]]
# change everytime though

You can limit the sub arrays size by replacing the a.size with 3 or anything you want.

Upvotes: 3

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