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{
"data": {
"question": {
"questionId": "2493",
"questionFrontendId": "2415",
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"title": "Reverse Odd Levels of Binary Tree",
"titleSlug": "reverse-odd-levels-of-binary-tree",
"content": "<p>Given the <code>root</code> of a <strong>perfect</strong> binary tree, reverse the node values at each <strong>odd</strong> level of the tree.</p>\n\n<ul>\n\t<li>For example, suppose the node values at level 3 are <code>[2,1,3,4,7,11,29,18]</code>, then it should become <code>[18,29,11,7,4,3,1,2]</code>.</li>\n</ul>\n\n<p>Return <em>the root of the reversed tree</em>.</p>\n\n<p>A binary tree is <strong>perfect</strong> if all parent nodes have two children and all leaves are on the same level.</p>\n\n<p>The <strong>level</strong> of a node is the number of edges along the path between it and the root node.</p>\n\n<p>&nbsp;</p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2022/07/28/first_case1.png\" style=\"width: 626px; height: 191px;\" />\n<pre>\n<strong>Input:</strong> root = [2,3,5,8,13,21,34]\n<strong>Output:</strong> [2,5,3,8,13,21,34]\n<strong>Explanation:</strong> \nThe tree has only one odd level.\nThe nodes at level 1 are 3, 5 respectively, which are reversed and become 5, 3.\n</pre>\n\n<p><strong class=\"example\">Example 2:</strong></p>\n<img alt=\"\" src=\"https://assets.leetcode.com/uploads/2022/07/28/second_case3.png\" style=\"width: 591px; height: 111px;\" />\n<pre>\n<strong>Input:</strong> root = [7,13,11]\n<strong>Output:</strong> [7,11,13]\n<strong>Explanation:</strong> \nThe nodes at level 1 are 13, 11, which are reversed and become 11, 13.\n</pre>\n\n<p><strong class=\"example\">Example 3:</strong></p>\n\n<pre>\n<strong>Input:</strong> root = [0,1,2,0,0,0,0,1,1,1,1,2,2,2,2]\n<strong>Output:</strong> [0,2,1,0,0,0,0,2,2,2,2,1,1,1,1]\n<strong>Explanation:</strong> \nThe odd levels have non-zero values.\nThe nodes at level 1 were 1, 2, and are 2, 1 after the reversal.\nThe nodes at level 3 were 1, 1, 1, 1, 2, 2, 2, 2, and are 2, 2, 2, 2, 1, 1, 1, 1 after the reversal.\n</pre>\n\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li>The number of nodes in the tree is in the range <code>[1, 2<sup>14</sup>]</code>.</li>\n\t<li><code>0 &lt;= Node.val &lt;= 10<sup>5</sup></code></li>\n\t<li><code>root</code> is a <strong>perfect</strong> binary tree.</li>\n</ul>\n",
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"lang": "C++",
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"code": "/**\n * Definition for a binary tree node.\n * struct TreeNode {\n * int val;\n * TreeNode *left;\n * TreeNode *right;\n * TreeNode() : val(0), left(nullptr), right(nullptr) {}\n * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}\n * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}\n * };\n */\nclass Solution {\npublic:\n TreeNode* reverseOddLevels(TreeNode* root) {\n \n }\n};",
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"lang": "Java",
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"code": "/**\n * Definition for a binary tree node.\n * public class TreeNode {\n * int val;\n * TreeNode left;\n * TreeNode right;\n * TreeNode() {}\n * TreeNode(int val) { this.val = val; }\n * TreeNode(int val, TreeNode left, TreeNode right) {\n * this.val = val;\n * this.left = left;\n * this.right = right;\n * }\n * }\n */\nclass Solution {\n public TreeNode reverseOddLevels(TreeNode root) {\n \n }\n}",
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"lang": "Python",
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"code": "# Definition for a binary tree node.\n# class TreeNode(object):\n# def __init__(self, val=0, left=None, right=None):\n# self.val = val\n# self.left = left\n# self.right = right\nclass Solution(object):\n def reverseOddLevels(self, root):\n \"\"\"\n :type root: Optional[TreeNode]\n :rtype: Optional[TreeNode]\n \"\"\"\n ",
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"code": "# Definition for a binary tree node.\n# class TreeNode:\n# def __init__(self, val=0, left=None, right=None):\n# self.val = val\n# self.left = left\n# self.right = right\nclass Solution:\n def reverseOddLevels(self, root: Optional[TreeNode]) -> Optional[TreeNode]:\n ",
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"lang": "C",
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"code": "/**\n * Definition for a binary tree node.\n * struct TreeNode {\n * int val;\n * struct TreeNode *left;\n * struct TreeNode *right;\n * };\n */\nstruct TreeNode* reverseOddLevels(struct TreeNode* root) {\n \n}",
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"code": "/**\n * Definition for a binary tree node.\n * public class TreeNode {\n * public int val;\n * public TreeNode left;\n * public TreeNode right;\n * public TreeNode(int val=0, TreeNode left=null, TreeNode right=null) {\n * this.val = val;\n * this.left = left;\n * this.right = right;\n * }\n * }\n */\npublic class Solution {\n public TreeNode ReverseOddLevels(TreeNode root) {\n \n }\n}",
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"code": "/**\n * Definition for a binary tree node.\n * function TreeNode(val, left, right) {\n * this.val = (val===undefined ? 0 : val)\n * this.left = (left===undefined ? null : left)\n * this.right = (right===undefined ? null : right)\n * }\n */\n/**\n * @param {TreeNode} root\n * @return {TreeNode}\n */\nvar reverseOddLevels = function(root) {\n \n};",
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"code": "/**\n * Definition for a binary tree node.\n * class TreeNode {\n * val: number\n * left: TreeNode | null\n * right: TreeNode | null\n * constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {\n * this.val = (val===undefined ? 0 : val)\n * this.left = (left===undefined ? null : left)\n * this.right = (right===undefined ? null : right)\n * }\n * }\n */\n\nfunction reverseOddLevels(root: TreeNode | null): TreeNode | null {\n \n};",
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"lang": "PHP",
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"code": "/**\n * Definition for a binary tree node.\n * class TreeNode {\n * public $val = null;\n * public $left = null;\n * public $right = null;\n * function __construct($val = 0, $left = null, $right = null) {\n * $this->val = $val;\n * $this->left = $left;\n * $this->right = $right;\n * }\n * }\n */\nclass Solution {\n\n /**\n * @param TreeNode $root\n * @return TreeNode\n */\n function reverseOddLevels($root) {\n \n }\n}",
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"lang": "Swift",
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"code": "/**\n * Definition for a binary tree node.\n * public class TreeNode {\n * public var val: Int\n * public var left: TreeNode?\n * public var right: TreeNode?\n * public init() { self.val = 0; self.left = nil; self.right = nil; }\n * public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }\n * public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {\n * self.val = val\n * self.left = left\n * self.right = right\n * }\n * }\n */\nclass Solution {\n func reverseOddLevels(_ root: TreeNode?) -> TreeNode? {\n \n }\n}",
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"lang": "Kotlin",
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"code": "/**\n * Example:\n * var ti = TreeNode(5)\n * var v = ti.`val`\n * Definition for a binary tree node.\n * class TreeNode(var `val`: Int) {\n * var left: TreeNode? = null\n * var right: TreeNode? = null\n * }\n */\nclass Solution {\n fun reverseOddLevels(root: TreeNode?): TreeNode? {\n \n }\n}",
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"lang": "Dart",
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"code": "/**\n * Definition for a binary tree node.\n * class TreeNode {\n * int val;\n * TreeNode? left;\n * TreeNode? right;\n * TreeNode([this.val = 0, this.left, this.right]);\n * }\n */\nclass Solution {\n TreeNode? reverseOddLevels(TreeNode? root) {\n \n }\n}",
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"lang": "Go",
"langSlug": "golang",
"code": "/**\n * Definition for a binary tree node.\n * type TreeNode struct {\n * Val int\n * Left *TreeNode\n * Right *TreeNode\n * }\n */\nfunc reverseOddLevels(root *TreeNode) *TreeNode {\n \n}",
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"lang": "Ruby",
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"code": "# Definition for a binary tree node.\n# class TreeNode\n# attr_accessor :val, :left, :right\n# def initialize(val = 0, left = nil, right = nil)\n# @val = val\n# @left = left\n# @right = right\n# end\n# end\n# @param {TreeNode} root\n# @return {TreeNode}\ndef reverse_odd_levels(root)\n \nend",
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"lang": "Scala",
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"code": "/**\n * Definition for a binary tree node.\n * class TreeNode(_value: Int = 0, _left: TreeNode = null, _right: TreeNode = null) {\n * var value: Int = _value\n * var left: TreeNode = _left\n * var right: TreeNode = _right\n * }\n */\nobject Solution {\n def reverseOddLevels(root: TreeNode): TreeNode = {\n \n }\n}",
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"lang": "Rust",
"langSlug": "rust",
"code": "// Definition for a binary tree node.\n// #[derive(Debug, PartialEq, Eq)]\n// pub struct TreeNode {\n// pub val: i32,\n// pub left: Option<Rc<RefCell<TreeNode>>>,\n// pub right: Option<Rc<RefCell<TreeNode>>>,\n// }\n// \n// impl TreeNode {\n// #[inline]\n// pub fn new(val: i32) -> Self {\n// TreeNode {\n// val,\n// left: None,\n// right: None\n// }\n// }\n// }\nuse std::rc::Rc;\nuse std::cell::RefCell;\nimpl Solution {\n pub fn reverse_odd_levels(root: Option<Rc<RefCell<TreeNode>>>) -> Option<Rc<RefCell<TreeNode>>> {\n \n }\n}",
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"lang": "Racket",
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"code": "; Definition for a binary tree node.\n#|\n\n; val : integer?\n; left : (or/c tree-node? #f)\n; right : (or/c tree-node? #f)\n(struct tree-node\n (val left right) #:mutable #:transparent)\n\n; constructor\n(define (make-tree-node [val 0])\n (tree-node val #f #f))\n\n|#\n\n(define/contract (reverse-odd-levels root)\n (-> (or/c tree-node? #f) (or/c tree-node? #f))\n )",
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"code": "%% Definition for a binary tree node.\n%%\n%% -record(tree_node, {val = 0 :: integer(),\n%% left = null :: 'null' | #tree_node{},\n%% right = null :: 'null' | #tree_node{}}).\n\n-spec reverse_odd_levels(Root :: #tree_node{} | null) -> #tree_node{} | null.\nreverse_odd_levels(Root) ->\n .",
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"code": "# Definition for a binary tree node.\n#\n# defmodule TreeNode do\n# @type t :: %__MODULE__{\n# val: integer,\n# left: TreeNode.t() | nil,\n# right: TreeNode.t() | nil\n# }\n# defstruct val: 0, left: nil, right: nil\n# end\n\ndefmodule Solution do\n @spec reverse_odd_levels(root :: TreeNode.t | nil) :: TreeNode.t | nil\n def reverse_odd_levels(root) do\n \n end\nend",
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"hints": [
"Try to solve recursively for each level independently.",
"While performing a depth-first search, pass the left and right nodes (which should be paired) to the next level. If the current level is odd, then reverse their values, or else recursively move to the next level."
],
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"status": null,
"sampleTestCase": "[2,3,5,8,13,21,34]",
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