如何转换此数组，以便每个元素代表前面元素的累积值？

Question

  

可能重复：
  Cumulative array sum in Ruby

我有一个像这样的整数数组

[20, 25, 40, 60]

如何将其变成一个数组，每个元素代表之前元素的累积值，包括它自己？

[20, 45, 85, 145]

我正在使用Rails 3.2.0＆amp;红宝石1.9.3

Answer 1

s = 0
[20, 25, 40, 60].map{|e| s += e}

Answer 2

[20, 25, 40, 60].reduce([]) do |arr, v|
  arr << (arr.last || 0) + v
end

或丑陋一个班轮。

[20, 25, 40, 60].reduce([0]){ |a, v| a << a[-1] + v }[1..-1]

Answer 3

array = [20, 25, 40, 60]
(array.size - 1).times { |i| array[i + 1] += array[i] }
puts array
# => [20, 45, 85, 145]

Answer 4

Matlab的：

B = cumsum(A)

红宝石：

class Array
  def ruby_cumsum!
    (1..size-1).each {|i| self[i] += self[i-1] }
    self
  end
end

Answer 5

arr.each_with_index.map{|x, i| x + (i==0 ? 0 : arr[0..i-1].inject(:+))}

=> [20, 45, 85, 145]

Answer 6

arr = [20, 25, 40, 60]
first = []
sum = 0

arr.each do |e|
  sum += e
  first << sum
end
puts first