按下一个 id Ramda.js 排序双向链表

Question

我想按 next_id 值对双向链表进行排序。

我的 DLL：

const dll = [
  {id: '22', prev_id: '41', next_id: '45'},
  {id: '45', prev_id: '22', next_id: null},
  {id: '41', prev_id: '14', next_id: '22'},
  {id: '14', prev_id: null, next_id: '41'},
]

结果：

const dll_result = [
  {id: '14', prev_id: null, next_id: '41'}, // next item - 41
  {id: '41', prev_id: '14', next_id: '22'}, // next item - 22
  {id: '22', prev_id: '41', next_id: '45'}, // next item - 45
  {id: '45', prev_id: '22', next_id: null},
]

我知道对 DLL 进行排序可能没有意义，但在我的情况下，我需要使用 next_id.

按顺序可视化数组中的数据

P.S. 知道原生解决方案就好了，然后我可以尝试自己转换成 Ramda.js

Answer 1

原生方法

您可以按 id 排序并选择最低的 id 作为所需输出的第一个元素，然后您可以通过使用属性 [=13 查找下一个节点来推送下一个元素=].

const dll = [{id: '22', prev_id: '41', next_id: '45'},{id: '45', prev_id: '22', next_id: null},{id: '41', prev_id: '14', next_id: '22'},{id: '14', prev_id: null, next_id: '41'}],
      result = [[...dll].sort((a, b) => a.id - b.id).shift()];

dll.forEach(() => result.push(dll.find(({id}) => id === result[result.length - 1].next_id)));
console.log(result);

Answer 2

通过id创建项目索引，找到第一个项目（prev_id === null），然后用while循环迭代，并将当前对象压入结果数组:

const findStart = R.find(R.propEq('prev_id', null))
const indexById = R.indexBy(R.prop('id'))

const sortByNextId = arr => {
  const index = indexById(arr)
  let current = findStart(arr)
  
  const sorted = []
  
  while(current) {
    sorted.push(current)
    current = index[current.next_id]
  }
  
  return sorted
}

const dll = [
  {id: '22', prev_id: '41', next_id: '45'},
  {id: '45', prev_id: '22', next_id: null},
  {id: '41', prev_id: '14', next_id: '22'},
  {id: '14', prev_id: null, next_id: '41'},
]

const result = sortByNextId(dll)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.0/ramda.js"></script>

按下一个 id Ramda.js 排序双向链表

Sort doubly linked list by next id Ramda.js

javascript

arrays

sorting

doubly-linked-list

ramda.js