Question

Given a sorted array of n integers, like the following:

ary = [3, 5, 6, 9, 14]

I need to calculate the difference between each element and the next element in the array. Using the example above, I would end up with:

[2, 1, 3, 5]

The beginning array may have 0, 1 or many elements in it, and the numbers I’ll be handling will be much larger (I’ll be using epoch timestamps). I’ve tried the following:

times = @messages.map{|m| m.created_at.to_i}
left  = times[1..times.length-1]
right = times[0..times.length-2]
differences = left.zip(right).map { |x| x[0]-x[1]}

But my solution above is both not optimal, and not ideal. Can anyone give me a hand?

Answer 1

ary = [3, 5, 6, 9, 14] #=> [3, 5, 6, 9, 14]
ary.each_cons(2).map { |a,b| b-a } #=> [2, 1, 3, 5]

Edit:
Replaced inject with map.