转换2元数组的数组的一个哈希,其中重复键追加额外的价值 [英] Convert array of 2-element arrays into a hash, where duplicate keys append additional values
本文介绍了转换2元数组的数组的一个哈希,其中重复键追加额外的价值的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
例如
给定一个数组:
阵列= [[:一,:B],[:一,:C],[C::B]]
返回下面的哈希:
散= {:A => [:B,:C]:C => [:B]}
散散= [阵列]
覆盖previous协会,生产:
散= {:A => C:C => :B}
解决方案
使用功能性婴儿的步骤:
IRB:01.0>数组= [[:一,:B],[:一,:C],[:C,:B]]
#=> [[:一,:B],[:一,:C],[:C,:B]]IRB:02.0> array.group_by(安培;:先)
#=> {:一个= GT; [[:一,:B],[:一,:C],:C => [:C,:B]]}IRB:03.0> array.group_by(安培;:第一).MAP {| K,A | [K,a.map(安培;:最后一个)]}
#=> [[:一,[:B,:C],[C:[:B]]IRB:04.0>哈希[array.group_by(安培;:第一).MAP {| K,A | [K,a.map(安培;:最后一个)]}]
#=> {:A => [:B,:C]:C =>:B]}
使用命令式编程风格:
IRB:10.0> H = {Hash.new | H,K | H [k]的= []}
#=> {}IRB:11.0> array.each {| K,V | H [k]的&下;&下; v}
#=> [[:一,:B],[:一,:C],[:C,:B]]IRB:12.0> H
#=> {:A => [:B,:C]:C =>:B]}
作为当务之急单行:
IRB:13.0> H = {Hash.new | H,K | H [k]的= []} .tap {| H | array.each {| K,V | H [k]的&下;&下; V}}
#=> {:A => [:B,:C]:C =>:B]}
或者用大家最喜欢的注
:
IRB:14.0> array.inject(Hash.new {| H,K | H [K] = []}){| h时,(K,V)| H [k]的&下;&下;伏; H }
#=> {:A => [:B,:C]:C =>:B]}
如果你真的想拥有单一数值没有发生碰撞为一个数组,您可以取消阵列他们作为一个后处理步骤,或者使用不同的哈希积累的策略,只有在产生碰撞的数组。另外,包装你的头周围这样的:
IRB:17.0>哈希= array.map {|对|哈希[*一双]}#合并许多小型哈希
#=> [{:A =>:B},{:A =>:C},{:C =>:B}]IRB:18.0> hashes.inject {| H1,H2 | h1.merge(H2){| * A |一个[1,2]}}
#=> {:A => [:B,:C]:C =>:B}
For example
Given an array:
array = [[:a,:b],[:a,:c],[:c,:b]]
Return the following hash:
hash = { :a => [:b,:c] , :c => [:b] }
hash = Hash[array]
overwrites previous associations, producing:
hash = { :a => :c , :c => :b }
解决方案
Using functional baby steps:
irb:01.0> array = [[:a,:b],[:a,:c],[:c,:b]]
#=> [[:a, :b], [:a, :c], [:c, :b]]
irb:02.0> array.group_by(&:first)
#=> {:a=>[[:a, :b], [:a, :c]], :c=>[[:c, :b]]}
irb:03.0> array.group_by(&:first).map{ |k,a| [k,a.map(&:last)] }
#=> [[:a, [:b, :c]], [:c, [:b]]]
irb:04.0> Hash[ array.group_by(&:first).map{ |k,a| [k,a.map(&:last)] } ]
#=> {:a=>[:b, :c], :c=>[:b]}
Using imperative style programming:
irb:10.0> h = Hash.new{ |h,k| h[k]=[] }
#=> {}
irb:11.0> array.each{ |k,v| h[k] << v }
#=> [[:a, :b], [:a, :c], [:c, :b]]
irb:12.0> h
#=> {:a=>[:b, :c], :c=>[:b]}
As an imperative one-liner:
irb:13.0> h = Hash.new{ |h,k| h[k]=[] }.tap{ |h| array.each{ |k,v| h[k] << v } }
#=> {:a=>[:b, :c], :c=>[:b]}
Or using everyone's favorite inject
:
irb:14.0> array.inject(Hash.new{ |h,k| h[k]=[] }){ |h,(k,v)| h[k] << v; h }
#=> {:a=>[:b, :c], :c=>[:b]}
If you really want to have single values not collided as an array, you can either un-array them as a post-processing step, or use a different hash accumulation strategy that only creates an array upon collision. Alternatively, wrap your head around this:
irb:17.0> hashes = array.map{ |pair| Hash[*pair] } # merge many mini hashes
#=> [{:a=>:b}, {:a=>:c}, {:c=>:b}]
irb:18.0> hashes.inject{ |h1,h2| h1.merge(h2){ |*a| a[1,2] } }
#=> {:a=>[:b, :c], :c=>:b}
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