在Ruby中找出一个时间段和一组范围差异的有效方法

发布时间：2020-12-17 04:13:48 所属栏目：百科来源：网络整理

导读：我在 Ruby中有很多时间范围： period = Time.parse('8:00am')..Time.parse('8:00pm')incidents = [ Time.parse('7:00am')..Time.parse('9:00am'),Time.parse('1:00pm')..Time.parse('3:00pm'),Time.parse('1:30pm')..Time.parse('3:30pm'),Time.parse('7:00p

我在 Ruby中有很多时间范围：

period = Time.parse('8:00am')..Time.parse('8:00pm')
incidents = [
  Time.parse('7:00am')..Time.parse('9:00am'),Time.parse('1:00pm')..Time.parse('3:00pm'),Time.parse('1:30pm')..Time.parse('3:30pm'),Time.parse('7:00pm')..Time.parse('9:00pm'),]

我正试图在这段时间内获得一系列事件免费块.对于上面那个是：

[
  Time.parse('9:00am')..Time.parse('1:00pm')
  Time.parse('3:30pm')..Time.parse('7:00pm')
]

从上面可以看出事件在这段时间之外重叠或延伸.范围或类似的任何操作是否会使这种计算更简单？

解决方法

令full_range为范围,范围为范围数组,分别代表提问者所称的期间和事件.我假设所有范围中包含的元素都可以是任何对象,只要它们可以与适用的类’方法< =>进行比较.并且已包含模块 Comparable.

码

def uncovered_ranges(full_range,ranges)
  ucrs = [full_range]
  ranges.each do |r|
    ucrs = ucrs.flat_map do |ucr|
      if ucr.first >= r.last || ucr.last <= r.first
        ucr 
      elsif r.first <= ucr.first && r.last >= ucr.last
        nil
      elsif r.first <= ucr.first && r.last < ucr.last
        r.last..ucr.last
      elsif r.first > ucr.first && r.last >= ucr.last
        ucr.first..r.first
      else
        [ucr.first..r.first,r.last..ucr.last]
      end
    end.compact
  end
  ucrs
end

例子

full_range = 1..20
ranges = [3..4,6..8,10..12,8..14,16..17,20..20]   

uncovered_ranges(full_range,ranges)
  #=> [1..3,4..6,14..16,17..20]

require 'time'

full_range = Time.parse('8:00am')..Time.parse('8:00pm')
  #=> 2016-12-22 08:00:00 -0800..2016-12-22 20:00:00 -0800 

ranges = [
  Time.parse('7:00am')..Time.parse('9:00am'),]
  #=> [2016-12-22 07:00:00 -0800..2016-12-22 09:00:00 -0800,#    2016-12-22 13:00:00 -0800..2016-12-22 15:00:00 -0800,#    2016-12-22 13:30:00 -0800..2016-12-22 15:30:00 -0800,#    2016-12-22 19:00:00 -0800..2016-12-22 21:00:00 -0800] 

uncovered_ranges(full_range,ranges)
  #=> [2016-12-22 09:00:00 -0800..2016-12-22 13:00:00 -0800,#    2016-12-22 15:30:00 -0800..2016-12-22 19:00:00 -0800]

说明

对我来说,解释正在发生的事情的最简单和最直接的方式可能是插入一些puts语句并运行上面第一个例子的代码.

def uncovered_ranges(full_range,ranges)
  ucrs = [full_range]
  puts "ucrs initially=#{ucrs}"
  ranges.each do |r|
    puts "ncovering range r=#{r}"
    ucrs = ucrs.flat_map do |ucr|
      puts "  range uncovered so far ucr=#{ucr}"
      if ucr.first >= r.last || ucr.last <= r.first
        puts "  in if #1,returning #{ucr}"
        ucr 
      elsif r.first <= ucr.first && r.last >= ucr.last
        puts "  in if #2,returning nil"
        nil
      elsif r.first <= ucr.first && r.last < ucr.last
        puts "  in if #3,returning #{r.last..ucr.last}"
        r.last..ucr.last
      elsif r.first > ucr.first && r.last >= ucr.last
        puts "  in if #4,returning #{ucr.first..r.first}"
        ucr.first..r.first
      else
        puts "  in else,returning #{[ucr.first..r.first,r.last..ucr.last]}"
       [ucr.first..r.first,r.last..ucr.last]
      end
    end.tap { |u| puts "ucrs after processing range #{r}=#{u}" }.
        compact.
        tap { |u| puts "ucrs after compact=#{u}" }
  end
  ucrs
end

uncovered_ranges 1..20,[3..4,20..20]

打印以下内容.

ucrs initially=[1..20]

covering range r=3..4
  range uncovered so far ucr=1..20
  in else,returning [1..3,4..20]
ucrs after processing range 3..4=[1..3,4..20]
ucrs after compact=[1..3,4..20]

covering range r=6..8
  range uncovered so far ucr=1..3
  in if #1,returning 1..3
  range uncovered so far ucr=4..20
  in else,returning [4..6,8..20]
ucrs after processing range 6..8=[1..3,8..20]
ucrs after compact=[1..3,8..20]

covering range r=10..12
  range uncovered so far ucr=1..3
  in if #1,returning 1..3
  range uncovered so far ucr=4..6
  in if #1,returning 4..6
  range uncovered so far ucr=8..20
  in else,returning [8..10,12..20]
ucrs after processing range 10..12=[1..3,8..10,12..20]
ucrs after compact=[1..3,12..20]

covering range r=8..14
  range uncovered so far ucr=1..3
  in if #1,returning 4..6
  range uncovered so far ucr=8..10
  in if #2,returning nil
  range uncovered so far ucr=12..20
  in if #3,returning 14..20
ucrs after processing range 8..14=[1..3,nil,14..20]
ucrs after compact=[1..3,14..20]

covering range r=16..17
  range uncovered so far ucr=1..3
  in if #1,returning 4..6
  range uncovered so far ucr=14..20
  in else,returning [14..16,17..20]
ucrs after processing range 16..17=[1..3,17..20]
ucrs after compact=[1..3,17..20]

covering range r=20..20
  range uncovered so far ucr=1..3
  in if #1,returning 4..6
  range uncovered so far ucr=14..16
  in if #1,returning 14..16
  range uncovered so far ucr=17..20
  in if #1,returning 17..20
ucrs after processing range 20..20=[1..3,17..20]
  #=> [1..3,17..20]

（编辑：李大同）

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