LeetCode本地测试二叉树 （ 标准格式/串行化格式 数组转为二叉树 ）例：[1, null, 2, 3]

LeetCode 数组转二叉树

(参考文档)[www.xiabingbao.com/post/js/lee…]

// 二叉树
function TreeNode(val) {
  this.val = val;
  this.left = this.right = null;
}

// [1, null, 2, null, null, 3, null]是标准格式 数组->二叉树
function array2BinaryTree(arr, index = 0) {
  if (index >= arr.length || arr[index] === null) {
    return null;
  }

  const root = new TreeNode(arr[index]);
  root.left = array2BinaryTree(arr, 2 * index + 1);
  root.right = array2BinaryTree(arr, 2 * index + 2);

  return root;
}

// [1, null, 2, 3] 是串行化格式  数组->二叉树
function deserialize(data) {
  if (!data || data.length === 0) {
    return null;
  }

  let root = new TreeNode(data[0]);
  let queue = [root];
  let i = 1;

  while (i < data.length) {
    let node = queue.shift();

    if (data[i] !== null) {
      node.left = new TreeNode(data[i]);
      queue.push(node.left);
    }

    i++;

    if (i < data.length && data[i] !== null) {
      node.right = new TreeNode(data[i]);
      queue.push(node.right);
    }

    i++;
  }

  return root;
};