226. 翻转二叉树

给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。

示例 1：

输入：root = [4,2,7,1,3,6,9]
输出：[4,7,2,9,6,3,1]

示例 2：

 2
/ \
1 3

输入：root = [2,1,3]
输出：[2,3,1]

示例 3：
输入：root = []
输出：[]

提示：
树中节点数目范围在 [0, 100] 内
-100 <= Node.val <= 100

来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/invert-binary-tree

javascript

/**
 * 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 {TreeNode}
 */
var invertTree = function (root) {
  if (!root) return root
  if (root) {
    root.left && invertTree(root.left)
    root.right && invertTree(root.right)
    var temp = root.left
    root.left = root.right
    root.right = temp
  }
  return root
}

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

var n1 = new TreeNode(2)
var n2 = new TreeNode(1)
var n3 = new TreeNode(3)
n1.left = n2
// n1.right = n3

console.log(invertTree(n1))

// var n1 = new TreeNode(4)
// var n2 = new TreeNode(2)
// var n3 = new TreeNode(7)
// var n4 = new TreeNode(1)
// var n5 = new TreeNode(3)
// var n6 = new TreeNode(6)
// var n7 = new TreeNode(9)
// n1.left = n2
// n1.right = n3
// n2.left = n4
// n2.right = n5
// n3.left = n6
// n3.right = n7

// console.log(invertTree(null))

226. 翻转二叉树 #

226. 翻转二叉树