异常数据分组/转换

Question

我正在努力解决一个算法问题，如何转换或分组数据以获得指定的输出。

我的输入是一堆按给定顺序排列的消息（从最新到最旧）：

[
   {
      "id":5,
      "created_at":"2021-01-01 00:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":true,
      "meta_data":{
         
      }
   },
   {
      "id":4,
      "created_at":"2021-01-01 01:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":true,
      "meta_data":{
         
      }
   },
   {
      "id":3,
      "created_at":"2021-01-01 03:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":false,
      "meta_data":{
         
      }
   },
   {
      "id":2,
      "created_at":"2021-01-01 04:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":false,
      "meta_data":{
         
      }
   },
   {
      "id":1,
      "created_at":"2021-01-01 05:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":true,
      "meta_data":{
         
      }
   },
   {
      "id":0,
      "created_at":"2021-01-01 06:00:00",
      "message":"Lorem ipsum dolor sit amet...",
      "is_author":false,
      "meta_data":{
         
      }
   }
]

转换后的期望输出：

[
   {
      "is_author":true,
      "messages":[
         {
            "id":5,
            "created_at":"2021-01-01 00:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         },
         {
            "id":4,
            "created_at":"2021-01-01 01:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         }
      ]
   },
   {
      "is_author":false,
      "messages":[
         {
            "id":3,
            "created_at":"2021-01-01 03:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         },
         {
            "id":2,
            "created_at":"2021-01-01 04:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         }
      ]
   },
   {
      "is_author":true,
      "messages":[
         {
            "id":1,
            "created_at":"2021-01-01 05:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         }
      ]
   },
   {
      "is_author":false,
      "messages":[
         {
            "id":0,
            "created_at":"2021-01-01 06:00:00",
            "message":"Lorem ipsum dolor sit amet...",
            "meta_data":{
               
            }
         }
      ]
   }
]

如您所见，每次出现 is_author 参数都会创建一个新组来收集来自该作者的消息？

在JS或PHP中是否有任何有效的解决方案来转换此类数据？

Answer 1

const data=[{"id":5,"created_at":"2021-01-01 00:00:00","message":"Lorem ipsum dolor sit amet...","is_author":true,"meta_data":{}},{"id":4,"created_at":"2021-01-01 01:00:00","message":"Lorem ipsum dolor sit amet...","is_author":true,"meta_data":{}},{"id":3,"created_at":"2021-01-01 03:00:00","message":"Lorem ipsum dolor sit amet...","is_author":false,"meta_data":{}},{"id":2,"created_at":"2021-01-01 04:00:00","message":"Lorem ipsum dolor sit amet...","is_author":false,"meta_data":{}},{"id":1,"created_at":"2021-01-01 05:00:00","message":"Lorem ipsum dolor sit amet...","is_author":true,"meta_data":{}},{"id":0,"created_at":"2021-01-01 06:00:00","message":"Lorem ipsum dolor sit amet...","is_author":false,"meta_data":{}}];

const result = data.reduce((acc, item) => {
  const { is_author, ...rest } = item;
  // if is_author match with previous object
  if(acc.length && acc[acc.length-1].is_author === is_author){
    // copy previous messages, along with current item
    acc[acc.length-1].messages = [...acc[acc.length-1].messages, rest ];
  }else{
      acc.push({ is_author, messages: [ rest ] });
  }
  return acc;
}, []);

console.log(result);

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Answer 2

抽象一点可以说很多。在这里，我们希望在两个连续元素之间发生变化时拆分我们的数组。这是基本的分组，如果我们这样想，我们可以将它们的集合分层到该分组之上的单个 {is_author, messages} 对象中。

因此，我们可能会编写一个通用函数，将我们的数据拆分为子数组，只要之前和当前项目的某些函数 returns true。然后我们的主函数会调用它，传递一个函数来测试 is_author 属性是否不同，然后在 returns 之后重新格式化生成的组。它可能看起来像这样：

const splitWhenever = (pred) => (xs) =>
  xs .length == 0 ? [] : xs .slice (1) .reduce (
    ((xss, x, i) => pred (xs [i], x) 
       ? [...xss, [x]] 
       : [...xss .slice (0, -1), [... xss [xss .length - 1], x]]
    ), [[xs [0]]]
  )

const transform = (input) => splitWhenever ((x, y) => x.is_author != y.is_author) (input)
  .map ((xs => ({
    is_author: xs [0] .is_author, 
    messages: xs .map (({is_author, ...rest}) => rest)
  })))

const input = [{id: 5, created_at: "2021-01-01 00:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 4, created_at: "2021-01-01 01:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 3, created_at: "2021-01-01 03:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}, {id: 2, created_at: "2021-01-01 04:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}, {id: 1, created_at: "2021-01-01 05:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 0, created_at: "2021-01-01 06:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}]

console .log (transform (input))

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这比 navnath 的答案更复杂。但它建立在 splitWherever 的基础上，现在可以在此程序和其他程序中重复使用。

在 navnath 的回答中，OP 问道，“[W]如果我处理了一组数据并且应用程序加载了新数据 [...] 是否可以加入来自对象 id 6 到现有组？”我在那里评论了一个建议的更改，只对 navanth 的代码进行了微小的调整。但是重读之后，我认为这个新数据应该在现有数据之前。（因为现有的 id 是降序排列的，而新的比那些大。）这意味着我的建议可能不会这样做。

这里需要做更多的工作，因为我们已经将分组与重新格式化分开了。这个版本仍然使用相同的通用 splitWhenever，首先将现有结构展平为原始格式，添加新数据，然后运行重新开始。这听起来很浪费。也许是。更好的方法可能是简单地保留原始列表，在其前面添加，然后重新运行上面的方法。但由于我们的转换是可逆的，因此如果需要，这将起作用：

const splitWhenever = (fn) => (xs) =>
  xs .length == 0 ? [] : xs .slice (1) .reduce (
    ((xss, x, i) => fn (xs [i], x) 
       ? [...xss, [x]] 
       : [...xss .slice (0, -1), [... xss [xss .length - 1], x]]
    ), [[xs [0]]]
  )

const transform = (input, old = []) => splitWhenever ((x, y) => x.is_author != y.is_author) ([
  ...input, 
  ...old.flatMap (({is_author, messages}) => messages .map (msg => ({...msg, is_author})))
]).map ((xs => ({
  is_author: xs [0] .is_author, 
  messages: xs .map (({is_author, ...rest}) => rest)
})))

const input = [{id: 5, created_at: "2021-01-01 00:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 4, created_at: "2021-01-01 01:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 3, created_at: "2021-01-01 03:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}, {id: 2, created_at: "2021-01-01 04:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}, {id: 1, created_at: "2021-01-01 05:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}, {id: 0, created_at: "2021-01-01 06:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}]
const result = transform (input)
console .log ('Original data')
console .log (result)

const additional = [{id: 7, created_at: "2020-12-31 22:00:00", message: "Lorem ipsum dolor sit amet...", is_author: false, meta_data: {}}, {id: 6, created_at: "2020-12-31 22:00:00", message: "Lorem ipsum dolor sit amet...", is_author: true, meta_data: {}}]
const result2 = transform (additional, result)
console .log ('With additional results')
console .log (result2)

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异常数据分组/转换

Unusual data grouping / transformation

javascript

php

algorithm

grouping

transformation