如何使用groovy对列表进行分组 [英] How to group a list of list using groovy

问题描述

我有一个列表，我想按照marketName和commodityName分组，列出价格：
例如[Terra，Wheat，1000.0] - Terra是市场名称，Wheat是商品名称，1000.0是价格

  def marketCommodityGroup = [
 [Merkato，Wheat，1000.0]，
 [Shola，Wheat，1875.0]，
 [Merkato，Barley ，5000.0]，
 [Merkato，小麦，1000.0]，
 [Merkato，小麦，1500.0] 
] 
  

我希望输出为：

 <$ c $ 
 [Merkato：[Wheat：[1000.0,1000.0,1500.0]]]，
 [Merkato：[Barley：[5000.0]]]，
 [Shola：[Wheat：[1875.0]]] 
] 
  

解决方案

好吧，这里有一个方法。

  def mapped = marketCommodityGroup.groupBy { 
 [（it [0]）：it [1]] 
} .collect {k，v  - > 
 def grouping = k.find {true} 
 def prices = v.inject（[]）{acc，val  - > acc + val [2]} 
 [（grouping.key），[（grouping.value）：prices]] 
} .sort {left，right  - > 
 right [0]< => left [0] 
} .collect {
 [（it [0]）：it [1]] 
} 
  

• 第一个 groupBy 确实 通过市场名称和商品名称
  
• collect 创建除最终 k：v association：
  
  
  
  • grouping 是键映射拆分中的唯一条目，因此可以重新排序到期望的形式
  
  
  • 价格用非常方便的 inject 来完成，它是Groovy等同于折叠功能语言中的操作
  
  


• sort 用于按照指定的顺序翻转订单 - 必须确定实际的逻辑是什么，以便您可以替换它


• last collect 做最终的地图分配以获得确切的想要的表单





是的，它有点密集和神奇的，但你总是可以移动关闭def带有适当的描述性名称。

I have a list of list that I want to group by marketName and commodityName, by listing price: e.g. ["Terra", "Wheat", 1000.0] - "Terra" is Market name, "Wheat" is Commodity Name, 1000.0 is price

def marketCommodityGroup = [
                              ["Merkato", "Wheat", 1000.0],  
                              ["Shola", "Wheat", 1875.0],  
                              ["Merkato", "Barley", 5000.0],  
                              ["Merkato", "Wheat", 1000.0],  
                              ["Merkato", "Wheat", 1500.0] 
                           ] 

I would like the output to be:

[
   ["Merkato": ["Wheat" : [1000.0, 1000.0, 1500.0]]],
   ["Merkato": ["Barley": [5000.0]]],
   ["Shola": ["Wheat": [1875.0]]]
]

解决方案

Alright, here's one way of doing it.

def mapped = marketCommodityGroup.groupBy {
  [(it[0]) : it[1]]
}.collect { k,v ->
  def grouping = k.find { true }
  def prices = v.inject([]) { acc,val -> acc + val[2] }
  [ (grouping.key) , [ (grouping.value) : prices ] ]
}.sort { left, right ->
  right[0] <=> left[0]
}.collect {
  [(it[0]) : it[1] ]
}

• first groupBy does exactly what you said, it groups by the market name and commodity name
• collect creates the wanted structure excluding the final k:v association:
  • grouping is the only entry in the key map split so that it can be reordered to desired form
  • prices is done with the very handy inject which is Groovy's equivalent for the fold left operation in functional languages
• sort is for flipping the order as you specified - had to quess what the actual logic is so you may want to replace it
• last collect does the final map assignment to get the exact wanted form

Yes, it's a bit dense and magical but you can always move the closures to defs with proper, descriptive names.

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