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Asked: 2024-01-03 22:15:35 +0800 CST

检查数组的所有元素是否方向交替

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在 Ruby 中，我需要检查数组的所有元素是否在方向上交替，即前驱和后继是否大于或小于每个元素。

给出以下数组，结果必须如所示

[1,3,2,4,3]  # => true
[3,2,4,3,5]  # => true
[1,2,3,1,3]. # => false 
[1,2,2,1,3]. # => false

我得出了以下代码，它似乎有效，但它很漂亮或易于理解。

array.each_cons(2)     # get subsequent couple of items
  .map {|a,b| b-a}.    # get the difference between first and second
  .map {|n| n <=> 0}   # get the sign (-1/+1)
  .each_cons(2)        # get couple of signs
  .map {|a,b| a+b}     # sum each couple
  .uniq == [0]         # return true if all the couple are 0

有什么建议如何简化检查吗？

ruby

2 个回答

  1. Best Answer
    def alternate_direction?(arr)
  return true if arr.size < 3
  arr.each_cons(3) do |prev, curr, succ|
    return false unless (curr > prev && curr > succ) || (curr < prev && curr < succ)
  end
  true
end

    现在让我们尝试打印

    puts alternate_direction?([1,3,2,4,3])  # => true
puts alternate_direction?([3,2,4,3,5])  # => true
puts alternate_direction?([1,2,3,1,3])  # => false
puts alternate_direction?([1,2,2,1,3])  # => false
    • 4

  2. ...只是因为@Rajagopalan 已经采取了each_cons，

    def alt(arr)
  return true if arr.size < 3
  prev = arr[1]<=>arr[0]
  return false if prev.zero?
  (2..arr.size-1).all? do |i|
    prev = -prev
    (arr[i]<=>arr[i-1]) == prev
  end
end

    [[1,3,2,4,3], [3,2,4,3,5], [1,2,3,1,3], [1,2,2,1,3], [2,2,1,4,3], [2,3], [2], []].
  map { |a| alt(a) }
  #=> [true, true, false, false, false, true, true, true]
    • 1

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