2021-05-05 17:13:49 +00:00
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---
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id: 587d8259367417b2b2512c83
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2021-12-19 15:32:25 +00:00
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title: 反轉二叉樹
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2021-05-05 17:13:49 +00:00
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challengeType: 1
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forumTopicId: 301704
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dashedName: invert-a-binary-tree
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---
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# --description--
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2021-12-19 15:32:25 +00:00
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這裏我們將創建一個反轉二叉樹的函數。 給定二叉樹,我們希望生成一個新樹,它等效於該樹的鏡像。 與原始樹的中序遍歷相比,在倒轉樹上運行中序遍歷將以相反的順序探索節點。 在我們的二叉樹上編寫一個名爲 `invert` 的方法。 調用此方法應該反轉當前樹結構。 理想情況下,我們希望在線性時間內就地執行此操作。 也就是說,我們只訪問每個節點一次,我們在不使用任何額外內存的情況下修改現有的樹結構。 祝你好運!
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2021-05-05 17:13:49 +00:00
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# --hints--
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2021-12-19 15:32:25 +00:00
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存在 `BinarySearchTree` 數據結構。
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2021-05-05 17:13:49 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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}
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return typeof test == 'object';
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})()
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);
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```
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2021-12-19 15:32:25 +00:00
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二叉搜索樹有一個名爲 `invert` 的方法。
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2021-05-05 17:13:49 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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return typeof test.invert == 'function';
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})()
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);
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```
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2021-12-19 15:32:25 +00:00
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`invert` 方法正確地反轉樹結構。
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2021-05-05 17:13:49 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.invert !== 'function') {
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return false;
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}
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test.add(4);
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test.add(1);
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test.add(7);
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test.add(87);
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test.add(34);
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test.add(45);
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test.add(73);
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test.add(8);
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test.invert();
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return test.inorder().join('') == '877345348741';
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})()
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);
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```
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2021-12-19 15:32:25 +00:00
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反轉空樹應該返回 `null`。
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2021-05-05 17:13:49 +00:00
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```js
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assert(
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(function () {
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var test = false;
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if (typeof BinarySearchTree !== 'undefined') {
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test = new BinarySearchTree();
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} else {
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return false;
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}
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if (typeof test.invert !== 'function') {
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return false;
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}
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return test.invert() == null;
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})()
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);
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```
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# --seed--
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## --after-user-code--
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```js
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BinarySearchTree.prototype = Object.assign(
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BinarySearchTree.prototype,
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{
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add: function(value) {
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function searchTree(node) {
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if (value < node.value) {
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if (node.left == null) {
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node.left = new Node(value);
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return;
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} else if (node.left != null) {
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return searchTree(node.left)
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};
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} else if (value > node.value) {
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if (node.right == null) {
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node.right = new Node(value);
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return;
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} else if (node.right != null) {
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return searchTree(node.right);
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};
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} else {
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return null;
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};
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}
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var node = this.root;
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if (node == null) {
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this.root = new Node(value);
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return;
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} else {
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return searchTree(node);
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};
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},
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inorder: function() {
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if (this.root == null) {
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return null;
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} else {
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var result = new Array();
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function traverseInOrder(node) {
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if (node.left != null) {
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traverseInOrder(node.left);
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};
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result.push(node.value);
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if (node.right != null) {
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traverseInOrder(node.right);
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};
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}
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traverseInOrder(this.root);
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return result;
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};
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}
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}
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);
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```
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## --seed-contents--
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```js
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var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
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function Node(value) {
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this.value = value;
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this.left = null;
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this.right = null;
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}
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function BinarySearchTree() {
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this.root = null;
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// Only change code below this line
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// Only change code above this line
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}
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```
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# --solutions--
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```js
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var displayTree = (tree) => console.log(JSON.stringify(tree, null, 2));
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function Node(value) {
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this.value = value;
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this.left = null;
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this.right = null;
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}
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function BinarySearchTree() {
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this.root = null;
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// Only change code below this line
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this.invert = function(node = this.root) {
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if (node) {
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const temp = node.left;
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node.left = node.right;
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node.right = temp;
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this.invert(node.left);
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this.invert(node.right);
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}
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return node;
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}
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// Only change code above this line
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}
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```
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