77 lines
4.7 KiB
Markdown
77 lines
4.7 KiB
Markdown
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---
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id: 587d8258367417b2b2512c80
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title: Delete a Leaf Node in a Binary Search Tree
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challengeType: 1
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videoUrl: ''
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localeTitle: 删除二进制搜索树中的叶节点
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---
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## Description
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<section id="description">这是我们将在二叉搜索树中实现更难操作的三个挑战中的第一个:删除。删除很困难,因为删除节点会破坏树中的链接。必须仔细重新建立这些链接以确保维护二叉树结构。对于某些删除,这意味着必须重新排列树。通常,在尝试删除节点时,您将遇到以下三种情况之一:叶节点:要删除的目标没有子节点。一个孩子:要删除的目标只有一个孩子。两个子节点:要删除的目标有两个子节点。删除叶节点很简单,我们只需删除它。删除具有一个子节点的节点也相对容易,我们只需删除它并将其父节点链接到我们删除的节点的子节点。但是,删除具有两个子节点的节点更加困难,因为这会创建两个需要重新连接到父树的子节点。我们将在第三个挑战中看到如何处理这个案例。此外,在处理删除时,您需要注意一些边缘情况。如果树是空的怎么办?如果要删除的节点是根节点怎么办?如果树中只有两个元素怎么办?现在,让我们处理第一种删除叶节点的情况。说明:在我们的二叉树上创建一个名为<code>remove</code> 。我们将在这里为我们的删除操作构建逻辑。首先,您需要在remove中创建一个函数,该函数在当前树中找到我们尝试删除的节点。如果树中不存在该节点,则<code>remove</code>应返回<code>null</code> 。现在,如果目标节点是没有子节点的叶节点,则应将其父节点引用设置为<code>null</code> 。这有效地从树中删除节点。为此,您必须跟踪我们尝试删除的节点的父节点。创建一种跟踪目标节点具有的子节点数的方法也很有用,因为这将确定我们的删除属于哪种情况。我们将在下一次挑战中处理第二和第三个案例。祝你好运! </section>
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## Instructions
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<section id="instructions">
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: 存在<code>BinarySearchTree</code>数据结构。
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testString: 'assert((function() { var test = false; if (typeof BinarySearchTree !== "undefined") { test = new BinarySearchTree() }; return (typeof test == "object")})(), "The <code>BinarySearchTree</code> data structure exists.");'
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- text: 二叉搜索树有一个名为<code>remove</code>的方法。
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testString: 'assert((function() { var test = false; if (typeof BinarySearchTree !== "undefined") { test = new BinarySearchTree() } else { return false; }; return (typeof test.remove == "function")})(), "The binary search tree has a method called <code>remove</code>.");'
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- text: 尝试删除不存在的元素将返回<code>null</code> 。
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testString: 'assert((function() { var test = false; if (typeof BinarySearchTree !== "undefined") { test = new BinarySearchTree() } else { return false; }; if (typeof test.remove !== "function") { return false; }; return (test.remove(100) == null); })(), "Trying to remove an element that does not exist returns <code>null</code>.");'
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- text: 如果根节点没有子节点,则删除它会将根节点设置为<code>null</code> 。
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testString: 'assert((function() { var test = false; if (typeof BinarySearchTree !== "undefined") { test = new BinarySearchTree() } else { return false; }; if (typeof test.remove !== "function") { return false; }; test.add(500); test.remove(500); return (test.inorder() == null); })(), "If the root node has no children, deleting it sets the root to <code>null</code>.");'
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- text: <code>remove</code>方法从树中删除叶节点
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testString: 'assert((function() { var test = false; if (typeof BinarySearchTree !== "undefined") { test = new BinarySearchTree() } else { return false; }; if (typeof test.remove !== "function") { return false; }; test.add(5); test.add(3); test.add(7); test.add(6); test.add(10); test.add(12); test.remove(3); test.remove(12); test.remove(10); return (test.inorder().join("") == "567"); })(), "The <code>remove</code> method removes leaf nodes from the tree");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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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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// case 1: target has no children, change code below this line
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}
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```
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</div>
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### After Test
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<div id='js-teardown'>
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```js
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console.info('after the test');
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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