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// 实现一个方法，将下列数组转化为树形结构
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const nodes = [
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  { id: 3, name: '节点C', parentId: 1 },
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  { id: 6, name: '节点F', parentId: 3 },
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  { id: 0, name: 'root', parentId: null },
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  { id: 1, name: '节点A', parentId: 0 },
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  { id: 8, name: '节点H', parentId: 4 },
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  { id: 4, name: '节点D', parentId: 1 },
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  { id: 2, name: '节点B', parentId: 0 },
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  { id: 5, name: '节点E', parentId: 2 },
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  { id: 7, name: '节点G', parentId: 2 },
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  { id: 9, name: '节点I', parentId: 5 }
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];
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/**
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 * @desc 将数组转化为树形结构
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 * @param {Array} data 待转换的数组
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 */
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const convertToTree = (data) => {
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  let result;
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  let map = {};
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  data.forEach(item => {
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    map[item.id] = item;
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  });
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  data.forEach(item => {
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    let parent = map[item.parentId];
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    if (parent) {
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      (parent.children || (parent.children = [])).push(item);
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    } else {
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      // parentId为null说明是根节点，直接将其返回即可
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      result = item;
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    }
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  });
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  return result;
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};

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const treeData = {
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  id: 0,
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  name: 'root',
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  parentId: null,
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  children: [
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    {
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      id: 1, name: '节点A', parentId: 0, children: [
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        {
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          id: 3, name: '节点C', parentId: 1, children: [
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            { id: 6, name: '节点F', parentId: 3, children: [] }
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          ]
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        },
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        {
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          id: 4, name: '节点D', parentId: 1, children: [
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            { id: 8, name: '节点H', parentId: 4, children: [] }
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          ]
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        }
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      ]
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    },
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    {
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      id: 2, name: '节点B', parentId: 0, children: [
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        {
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          id: 5, name: '节点E', parentId: 2, children: [
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            { id: 9, name: '节点I', parentId: 5, children: [] }
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          ]
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        },
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        { id: 7, name: '节点G', parentId: 2, children: [] }
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      ]
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    },
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  ]
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};
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/**
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 * @desc 树形结构数据转为一维数组
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 * @param {Tree} data 树形结构的数据
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 * @returns {Array}
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 */
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const TreeToArr = (data) => {
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  if (!data.children) {
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    return data;
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  }
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  const res = [];
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  const traversalChildren = (children) => {
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    children.forEach(item => {
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      if (item.children) {
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        traversalChildren(item.children);
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        delete item.children;
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      }
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      res.push(item);
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    });
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  };
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  traversalChildren(data.children);
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  // 添加根节点
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  delete data.children;
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  res.push(data);
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  return res;
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};