134 lines
5.6 KiB
Markdown
134 lines
5.6 KiB
Markdown
---
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id: 8d1323c8c441eddfaeb5bdef
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title: Create a Set Class
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challengeType: 1
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---
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## Description
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<section id='description'>
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In this exercise we are going to create a class named <code>Set</code> to emulate an abstract data structure called "set". A set is like an array, but it cannot contain duplicate values. The typical use for a set is to simply check for the presence of an item.
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We can see how ES6 set object works in the example below-
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```js
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const set1 = new Set([1, 2, 3, 5, 5, 2, 0]);
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console.log(set1);
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// output: {1, 2, 3, 5, 0}
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console.log(set1.has(1));
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// output: true
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console.log(set1.has(6));
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// output: false
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```
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First, we will create an add method that adds a value to our set collection as long as the value does not already exist in the set.
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Then we will create a remove method that removes a value from the set collection if it already exists.
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And finally, we will create a size method that returns the number of elements inside the set collection.
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</section>
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## Instructions
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<section id='instructions'>
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Create an <code>add</code> method that adds a unique value to the set collection and returns <code>true</code> if the value was successfully added and <code>false</code> otherwise.
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Create a <code>remove</code> method that accepts a value and checks if it exists in the set. If it does, then this method should remove it from the set collection, and return <code>true</code>. Otherwise, it should return <code>false</code>.
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Create a <code>size</code> method that returns the size of the set collection.
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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: Your <code>Set</code> class should have an <code>add</code> method.
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testString: assert((function(){var test = new Set(); return (typeof test.add === 'function')}()), 'Your <code>Set</code> class should have an <code>add</code> method.');
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- text: Your <code>add</code> method should not add duplicate values.
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testString: assert((function(){var test = new Set(); test.add('a'); test.add('b'); test.add('a'); var vals = test.values(); return (vals[0] === 'a' && vals[1] === 'b' && vals.length === 2)}()), 'Your <code>add</code> method should not add duplicate values.');
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- text: Your <code>add</code> method should return <code>true</code> when a value has been successfully added.
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testString: assert((function(){var test = new Set(); var result = test.add('a'); return (result != undefined) && (result === true);}()), 'Your <code>add</code> method should return <code>true</code> when a value has been successfully added.');
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- text: Your <code>add</code> method should return <code>false</code> when a duplicate value is added.
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testString: assert((function(){var test = new Set(); test.add('a'); var result = test.add('a'); return (result != undefined) && (result === false);}()), 'Your <code>add</code> method should return <code>false</code> when a duplicate value is added.');
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- text: Your <code>Set</code> class should have a <code>remove</code> method.
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testString: assert((function(){var test = new Set(); return (typeof test.remove === 'function')}()), 'Your <code>Set</code> class should have a <code>remove</code> method.');
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- text: Your <code>remove</code> method should only remove items that are present in the set.
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testString: assert.deepEqual((function(){var test = new Set(); test.add('a');test.add('b');test.remove('c'); return test.values(); })(), ['a', 'b'], 'Your <code>remove</code> method should only remove items that are present in the set.');
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- text: Your <code>remove</code> method should remove the given item from the set.
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testString: assert((function(){var test = new Set(); test.add('a');test.add('b');test.remove('a'); var vals = test.values(); return (vals[0] === 'b' && vals.length === 1)}()), 'Your <code>remove</code> method should remove the given item from the set.');
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- text: Your <code>Set</code> class should have a <code>size</code> method.
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testString: assert((function(){var test = new Set(); return (typeof test.size === 'function')}()), 'Your <code>Set</code> class should have a <code>size</code> method.');
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- text: The <code>size</code> method should return the number of elements in the collection.
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testString: assert((function(){var test = new Set(); test.add('a');test.add('b');test.remove('a');return (test.size() === 1)}()), 'The <code>size</code> method should return the number of elements in the collection.');
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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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class Set {
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constructor() {
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// collection will hold our set
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this.collection = [];
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}
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// this method will check for the presence of an element and return true or false
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has(element) {
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return this.collection.indexOf(element) !== -1;
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}
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// this method will return all the values in the set
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values() {
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return this.collection;
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}
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// change code below this line
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// write your add method here
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// write your remove method here
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// write your size method here
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// 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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class Set {
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constructor() {
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this.collection = [];
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}
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has(element) {
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return this.collection.indexOf(element) !== -1;
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}
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values() {
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return this.collection;
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}
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add(element) {
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if (!this.has(element)) {
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this.collection.push(element);
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return true;
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} else {
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return false;
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}
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}
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remove(element) {
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if (this.has(element)) {
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let i = this.collection.indexOf(element);
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this.collection.splice(i, 1);
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return true;
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}
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return false;
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}
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size() {
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return this.collection.length;
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}
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}
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```
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</section>
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