leetcode-101 对称二叉树

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isSymmetric = function (root) {
  function helper(node1, node2) {
    if (!node1 && !node2) return true;
    if (!node1 || !node2) return false;
    return (
      node1.val === node2.val &&
      helper(node1.left, node2.right) &&
      helper(node1.right, node2.left)
    );
  }
  return helper(root.left, root.right);
};

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isSymmetric = function (root) {
  const queue = [[root.left, root.right]];
  while (queue.length) {
    const [node1, node2] = queue.shift();
    if (!node1 && !node2) continue;
    if (!node1 || !node2) return false;
    if (node1.val !== node2.val) return false;
    queue.push([node1.left, node2.right], [node1.right, node2.left]);
  }
  return true;
};