freeCodeCamp/curriculum/challenges/english/10-coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data.english.md

id, title, challengeType, isHidden, forumTopicId

id	title	challengeType	isHidden	forumTopicId
587d8254367417b2b2512c6f	Perform a Subset Check on Two Sets of Data	1	false	301707

Description

In this exercise, we are going to perform a subset test on 2 sets of data. We will create a method on our Set data structure called isSubsetOf. This will compare the first set against the second, and if the first set is fully contained within the second, it will return true. For example, if setA = ['a','b'] and setB = ['a','b','c','d'], then setA is a subset of setB, so setA.isSubsetOf(setB) should return true.

Instructions

Tests

tests:
  - text: Your <code>Set</code> class should have a <code>isSubsetOf</code> method.
    testString: assert((function(){var test = new Set(); return (typeof test.isSubsetOf === 'function')})());
  - text: The first Set() should be contained in the second Set
    testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setB.add('b'); setB.add('c'); setB.add('a'); setB.add('d'); var aIsSubsetOfB = setA.isSubsetOf(setB);return (aIsSubsetOfB === true)})());
  - text: <code>['a', 'b'].isSubsetOf(['a', 'b', 'c', 'd'])</code> should return <code>true</code>
    testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setB.add('a'); setB.add('b'); setB.add('c'); setB.add('d'); var aIsSubsetOfB = setA.isSubsetOf(setB); return (aIsSubsetOfB === true)})());
  - text: <code>['a', 'b', 'c'].isSubsetOf(['a', 'b'])</code> should return <code>false</code>
    testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setA.add('c'); setB.add('a'); setB.add('b'); var aIsSubsetOfB = setA.isSubsetOf(setB); return (aIsSubsetOfB === false)})());
  - text: <code>[].isSubsetOf([])</code> should return <code>true</code>
    testString: assert((function(){var setA = new Set(); var setB = new Set(); var aIsSubsetOfB = setA.isSubsetOf(setB); return (aIsSubsetOfB === true)})());
  - text: <code>['a', 'b'].isSubsetOf(['c', 'd'])</code> should return <code>false</code>
    testString: assert((function(){var setA = new Set(); var setB = new Set(); setA.add('a'); setA.add('b'); setB.add('c'); setB.add('d'); var aIsSubsetOfB = setA.isSubsetOf(setB); return (aIsSubsetOfB === false)})());

Challenge Seed

class Set {
  constructor() {
    // This will hold the set
    this.dictionary = {};
    this.length = 0;
  }
  // this method will check for the presence of an element and return true or false
  has(element) {
    return this.dictionary[element] !== undefined;
  }
  // this method will return all the values in the set
  values() {
    return Object.keys(this.dictionary);
  }
  // this method will add an element to the set
  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = true;
      this.length++;
      return true;
    }

    return false;
  }
  // this method will remove an element from a set
  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }
  // this method will return the size of the set
  size() {
    return this.length;
  }
  // This is our union method from that lesson
  union(set) {
    const newSet = new Set();
    this.values().forEach(value => {
      newSet.add(value);
    })
    set.values().forEach(value => {
      newSet.add(value);
    })

    return newSet;
  }
  // This is our intersection method from that lesson
  intersection(set) {
    const newSet = new Set();

    let largeSet;
    let smallSet;
    if (this.dictionary.length > set.length) {
      largeSet = this;
      smallSet = set;
    } else {
      largeSet = set;
      smallSet = this;
    }

    smallSet.values().forEach(value => {
      if (largeSet.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }
  // This is our difference method from that lesson
  difference(set) {
    const newSet = new Set();

    this.values().forEach(value => {
      if (!set.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }
  // change code below this line
  // change code above this line
}

Solution

class Set {
  constructor() {
    this.dictionary = {};
    this.length = 0;
  }

  has(element) {
    return this.dictionary[element] !== undefined;
  }

  values() {
    return Object.keys(this.dictionary);
  }

  add(element) {
    if (!this.has(element)) {
      this.dictionary[element] = true;
      this.length++;
      return true;
    }

    return false;
  }

  remove(element) {
    if (this.has(element)) {
      delete this.dictionary[element];
      this.length--;
      return true;
    }

    return false;
  }

  size() {
    return this.length;
  }

  union(set) {
    const newSet = new Set();
    this.values().forEach(value => {
      newSet.add(value);
    })
    set.values().forEach(value => {
      newSet.add(value);
    })

    return newSet;
  }

  intersection(set) {
    const newSet = new Set();

    let largeSet;
    let smallSet;
    if (this.dictionary.length > set.length) {
      largeSet = this;
      smallSet = set;
    } else {
      largeSet = set;
      smallSet = this;
    }

    smallSet.values().forEach(value => {
      if (largeSet.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }  

  difference(set) {
    const newSet = new Set();

    this.values().forEach(value => {
      if (!set.dictionary[value]) {
        newSet.add(value);
      }
    })

    return newSet;
  }

  isSubsetOf(set) {
    for(const value of this.values()){
      if(!set.dictionary[value]) return false;
    }
    return true
  }
}