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将leetcode中二叉树的数组结构转为真实的树结构

 2 years ago
source link: https://www.xiabingbao.com/post/js/leetcode-treenode-array.html
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将leetcode中二叉树的数组结构转为真实的树结构

蚊子前端博客
发布于 2021-06-07 17:39
将leetcode中二叉树的数组结构转为真实的树结构

我们在 LeetCode 上锻炼算法时，关于二叉树的题目，网站上给的都直接是一个数组，那么本地测试的时候，就很不方便。

官方文档中的解释是这样的：[请问 [1, null, 2, 3] 在二叉树测试用例中代表什么](https://support.leetcode-cn.com/hc/kb/article/1194353/)。

这里写了一个 js 方法，将数组转为二叉树结构：

function TreeNode(val) {
  this.val = val;
  this.left = this.right = null;
}

const array2binary = (arr) => {
  if (!arr || !arr.length) {
    return null;
  }
  let index = 0;
  const queue = [];
  const len = arr.length;
  const head = new TreeNode(arr[index]);
  queue.push(head);

  while (index < len) {
    index++;
    const parent = queue.shift();
    if (arr[index] !== null && arr[index] !== undefined) {
      const node = new TreeNode(arr[index]);
      parent.left = node;
      queue.push(node);
    }

    index++;
    if (arr[index] !== null && arr[index] !== undefined) {
      const node = new TreeNode(arr[index]);
      parent.right = node;
      queue.push(node);
    }
  }
  return head;
};
const root = array2binary([3, 9, 20, null, null, 15, 7]);

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