I have this array and need to replace its elements by the multiplication of its previous and next.
I do the following:
array.each_with_index{|element, index|
next_element = array[index+1]
previous_element = array[index-1]
}
array.map! {|a|
if a == array.first
a = a * next_element
elsif a == array.last
a = a * previous_element
else
a = next_element * previous_element
end
}
I expect the following result:
array = [4, 1, 6, 7, 9, 3, 0] #given array
array = [4, 24, 7, 54, 21, 0, 0] #array replaced
I get the following error:
undefined local variable or method `next_element' for Arrays:Class
Is there a easy way of getting the previous and next element of a given array element?
Am I using the array.map! method right?
This would work:
array = [4, 1, 6, 7, 9, 3, 0]
[nil, *array, nil].each_cons(3).map { |l, m, r| (l || m) * (r || m) }
#=> [4, 24, 7, 54, 21, 0, 0]
The array is surrounded by nil values, so each element has neighbors. each_cons(3) then yiels each element along with its neighbors to map which multiplies the left (l) with the right (r) neighbor, falling back to the middle element (m) if one of the neighbors happens to be nil.
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