/*
 * @lc app=leetcode.cn id=226 lang=javascript
 *
 * [226] 翻转二叉树
 */

// @lc code=start
/**
 * 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)
 * }
 */

function TreeNode(val, left, right) {
  this.val = val === undefined ? 0 : val;
  this.left = left === undefined ? null : left;
  this.right = right === undefined ? null : right;
}

let root = new TreeNode(
  1,
  undefined,
  new TreeNode(2, new TreeNode(3, undefined, undefined), undefined)
);

/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
var invertTree = function (root) {
  if (root === null) {
    return null;
  }

  var left = invertTree(root.left);
  var right = invertTree(root.right);
  root.left = right;
  root.right = left;

  return root;
};

// @lc code=end