Say I have an array: [1, 2, 3, 4, 5].
Given another array ([2, 4], for example), I would like to have a new array (or the initial array modified, doesn't matter) that looks like: [1, 3, 5, 2, 4]. So selected elements are moved to the end of the array.
Pushing the elements back is quite straight-forward, but how do I pop specific elements from an array?
a = [1, 2, 3, 4, 5]
b = [2, 4]
(a - b) + (b & a)
#=> [1, 3, 5, 2, 4]
a - b is the elements in a but not in b, while b & a is the elements that are common in both arrays. There goes your expected result.
(a-b)+(b&a) to save the order of elements in the second array. Though it depends on what OP desired.
a are not unique, the result might not be what is expected.
(a-b) + b
b = [4,2], and then (a-b) + b #=> [1, 3, 5, 4, 2] or (a-b) + (a&b) #=> [1, 3, 5, 2, 4] , depending on the desired order of the last two elements.In case if elements in a are not uniq (as mentioned by eugen) and it's important to remove only one element from b you could do something like:
a = [1, 2, 3, 2, 4, 5, 4, 2]
b = [2, 4, 7]
p (b&a).unshift(a.map{|el|
b.include?(el) ? begin b = b -[el]; nil end : el
}.compact).flatten
#=> [1, 3, 2, 5, 4, 2, 2, 4]
[4,2], should the result be[1, 3, 5, 2, 4]or[1, 3, 5, 4, 2], or either?