ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
165 lines
3.3 KiB
Markdown
165 lines
3.3 KiB
Markdown
---
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id: 587d8250367417b2b2512c5f
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title: Create a Stack Class
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challengeType: 1
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forumTopicId: 301633
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dashedName: create-a-stack-class
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---
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# --description--
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In the last section, we talked about what a stack is and how we can use an array to represent a stack. In this section, we will be creating our own stack class. Although you can use arrays to create stacks, sometimes it is best to limit the amount of control we have with our stacks. Apart from the `push` and `pop` method, stacks have other useful methods. Let's add a `peek`, `isEmpty`, and `clear` method to our stack class.
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# --instructions--
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Write a `push` method that pushes an element to the top of the stack, a `pop` method that removes and returns the element on the top of the stack, a `peek` method that looks at the top element in the stack, an `isEmpty` method that checks if the stack is empty, and a `clear` method that removes all elements from the stack. Normally stacks don't have this, but we've added a `print` helper method that console logs the collection.
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# --hints--
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Your `Stack` class should have a `push` method.
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```js
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assert(
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(function () {
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var test = new Stack();
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return typeof test.push === 'function';
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})()
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);
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```
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Your `Stack` class should have a `pop` method.
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```js
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assert(
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(function () {
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var test = new Stack();
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return typeof test.pop === 'function';
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})()
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);
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```
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Your `Stack` class should have a `peek` method.
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```js
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assert(
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(function () {
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var test = new Stack();
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return typeof test.peek === 'function';
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})()
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);
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```
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Your `Stack` class should have a `isEmpty` method.
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```js
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assert(
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(function () {
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var test = new Stack();
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return typeof test.isEmpty === 'function';
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})()
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);
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```
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Your `Stack` class should have a `clear` method.
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```js
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assert(
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(function () {
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var test = new Stack();
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return typeof test.clear === 'function';
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})()
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);
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```
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The `peek` method should return the top element of the stack
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```js
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assert(
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(function () {
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var test = new Stack();
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test.push('CS50');
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return test.peek() === 'CS50';
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})()
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);
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```
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The `pop` method should remove and return the top element of the stack
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```js
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assert(
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(function () {
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var test = new Stack();
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test.push('CS50');
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return test.pop() === 'CS50';
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})()
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);
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```
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The `isEmpty` method should return true if a stack does not contain any elements
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```js
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assert(
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(function () {
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var test = new Stack();
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return test.isEmpty();
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})()
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);
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```
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The `clear` method should remove all element from the stack
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```js
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assert(
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(function () {
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var test = new Stack();
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test.push('CS50');
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test.clear();
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return test.isEmpty();
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})()
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);
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```
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# --seed--
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## --seed-contents--
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```js
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function Stack() {
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var collection = [];
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this.print = function() {
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console.log(collection);
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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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# --solutions--
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```js
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class Stack {
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constructor() {
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this.collection = [];
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}
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print() {
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console.log(this.collection);
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}
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push(val) {
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this.collection.push(val);
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}
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pop() {
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return this.collection.pop();
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}
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peek() {
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return this.collection[this.collection.length - 1];
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}
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isEmpty() {
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return this.collection.length === 0;
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}
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clear() {
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return (this.collection.length = 0);
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}
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}
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```
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