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对称二叉树

2022/11/17

https://leetcode.cn/problems/symmetric-tree/

示例​

示例一​

输入：root = [1,2,2,3,4,4,3] 输出：true

示例二​

输入：root = [1,2,2,null,3,null,3] 输出：false

题解参考​

DFS​

/**
 * @param {TreeNode} root
 * @return {boolean}
 */
var isSymmetric = function (root) {
  if (root === null) {
    return true;
  }
  const dfs = (left, right) => {
    if (left === null && right === null) {
      return true;
    }
    if (left === null || right === null) {
      return false;
    }
    if (left.val !== right.val) {
      return false;
    }
    return dfs(left.left, right.right) && dfs(left.right, right.left);
  };

  return dfs(root.left, root.right);
};