93 lines
3.1 KiB
Markdown
93 lines
3.1 KiB
Markdown
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---
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id: 587d8252367417b2b2512c67
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title: Add Elements at a Specific Index in a Linked List
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challengeType: 1
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videoUrl: ''
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localeTitle: 在链接列表中的特定索引处添加元素
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---
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## Description
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<section id="description">让我们创建一个addAt（index，element）方法，在给定的索引处添加一个元素。就像我们如何删除给定索引处的元素一样，我们需要在遍历链表时跟踪currentIndex。当currentIndex与给定索引匹配时，我们需要重新分配上一个节点的下一个属性以引用新添加的节点。并且新节点应该引用currentIndex中的下一个节点。回到康加线的例子，一个新人想加入这条线，但他想加入中间。你处于中间位置，所以你要把手从你前面的人身上移开。新人走过去，把手放在你曾经牵过手的那个人身上，现在你已经掌握了新人。说明创建addAt（index，element）方法，该方法在给定索引处添加元素。如果无法添加元素，则返回false。注意请记住检查给定索引是否为负数或者是否长于链接列表的长度。 </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: 当给定索引为0时， <code>addAt</code>方法应重新分配<code>head</code>到新节点。
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testString: 'assert((function(){var test = new LinkedList(); test.add("cat"); test.add("dog"); test.addAt(0,"cat"); return test.head().element === "cat"}()), "Your <code>addAt</code> method should reassign <code>head</code> to the new node when the given index is 0.");'
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- text: 对于添加到链接列表的每个新节点， <code>addAt</code>方法应该将链表的长度增加一。
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testString: 'assert((function(){var test = new LinkedList(); test.add("cat"); test.add("dog"); test.addAt(0,"cat"); return test.size() === 3}()), "Your <code>addAt</code> method should increase the length of the linked list by one for each new node added to the linked list.");'
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- text: 如果无法添加节点，则<code>addAt</code>方法应返回<code>false</code> 。
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testString: 'assert((function(){var test = new LinkedList(); test.add("cat"); test.add("dog"); return (test.addAt(4,"cat") === false); }()), "Your <code>addAt</code> method should return <code>false</code> if a node was unable to be added.");'
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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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function LinkedList() {
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var length = 0;
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var head = null;
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var Node = function(element){
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this.element = element;
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this.next = null;
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};
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this.size = function(){
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return length;
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};
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this.head = function(){
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return head;
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};
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this.add = function(element){
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var node = new Node(element);
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if(head === null){
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head = node;
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} else {
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currentNode = head;
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while(currentNode.next){
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currentNode = currentNode.next;
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}
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currentNode.next = node;
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}
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length++;
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};
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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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</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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