拼多多笔试题-编程

【题目本意：将数组结构数据转成链表结构，当时没看懂…呜呜…】
输入：

var arr = [
   {id : 1, parents : null},
   {id : 2 , parents : 1},
   {id : 3 , parents : 2},
]

输出：

var obj = {
	obj1: {
		id:1,
		parents:null,
		charld:{
			id:2,
			parents:1,
			charld: {
				id:3,
				parents:2,
			}
		}
    }
}

function arrayTolist(ary) {
  if (!ary.length) {
    return null
  }
  var node
  var head = { id: ary[0].id, parents: null }
  var preNode = head
  for (var i = 1; i < ary.length; i++) {
    node = { id: ary[i].id, parents: preNode.id }
    preNode.child = node
    preNode = node
  }
  return head
}

PS：顺便实现链表转数组

function listToArray(obj) {
  if (!obj) {
    return []
  }
  var result = []
  while (obj) {
    result.push({ id: obj.id, parents: obj.parents })
    obj = obj.child
  }
  return result
}