From 56f6d4654ce5cc1e02ee8a0c2b67bf4e1d6a5b45 Mon Sep 17 00:00:00 2001
From: Keith Warter <kmwarter@gmail.com>
Date: Wed, 22 Apr 2020 13:44:50 -0700
Subject: [PATCH] fix(learn): update solutions in interview-prep challenges
 (#38430)

Co-authored-by: Tom <20648924+moT01@users.noreply.github.com>
Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
---
 .../create-a-set-class.english.md             |  74 +++--
 ...-difference-on-two-sets-of-data.english.md | 279 ++++++++++--------
 ...ubset-check-on-two-sets-of-data.english.md | 247 +++++++++++-----
 .../perform-a-union-on-two-sets.english.md    | 150 +++++-----
 ...ntersection-on-two-sets-of-data.english.md | 223 +++++++-------
 5 files changed, 581 insertions(+), 392 deletions(-)

diff --git a/curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md b/curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md
index 65b5a344cd..3931573a4b 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/data-structures/create-a-set-class.english.md
@@ -71,27 +71,31 @@ tests:
 
 ```js
 class Set {
-    constructor() {
-    // collection will hold our set
-    this.collection = [];
-    }
-    // this method will check for the presence of an element and return true or false
-    has(element) {
-        return this.collection.indexOf(element) !== -1;
-    }
-    // this method will return all the values in the set
-    values() {
-        return this.collection;
-    }
-    // change code below this line
+  constructor() {
+    // Dictionary will hold the items of our set
+    this.dictionary = {};
+    this.length = 0;
+  }
 
-    // write your add method here
+  // This method will check for the presence of an element and return true or false
+  has(element) {
+    return this.dictionary[element] !== undefined;
+  }
 
-    // write your remove method here
+  // This method will return all the values in the set as an array
+  values() {
+    return Object.keys(this.dictionary);
+  }
 
-    // write your size method here
+  // change code below this line
+  
+  // write your add method here
 
-    // change code above this line
+  // write your remove method here
+
+  // write your size method here
+
+  // change code above this line
 }
 ```
 
@@ -105,32 +109,40 @@ class Set {
 ```js
 class Set {
   constructor() {
-    this.collection = [];
+    this.dictionary = {};
+    this.length = 0;
   }
+
   has(element) {
-    return this.collection.indexOf(element) !== -1;
+    return this.dictionary[element] !== undefined;
   }
+
   values() {
-    return this.collection;
+    return Object.keys(this.dictionary);
   }
+
   add(element) {
     if (!this.has(element)) {
-      this.collection.push(element);
-      return true;
-    } else {
-      return false;
-    }
-  }
-  remove(element) {
-    if (this.has(element)) {
-      let i = this.collection.indexOf(element);
-      this.collection.splice(i, 1);
+      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.collection.length;
+    return this.length;
   }
 }
 ```
diff --git a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-difference-on-two-sets-of-data.english.md b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-difference-on-two-sets-of-data.english.md
index 5e6d8cc5f5..4f22b89699 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-difference-on-two-sets-of-data.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-difference-on-two-sets-of-data.english.md
@@ -36,64 +36,80 @@ tests:
 <div id='js-seed'>
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-    // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-    // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the collection
-    this.size = function() {
-        return collection.length;
-    };
-    // this method will return the union of two sets
-    this.union = function(otherSet) {
-        var unionSet = new Set();
-        var firstSet = this.values();
-        var secondSet = otherSet.values();
-        firstSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        secondSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        return unionSet;
-    };
-    // this method will return the intersection of two sets as a new set
-    this.intersection = function(otherSet) {
-        var intersectionSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e){
-            if(otherSet.has(e)){
-                intersectionSet.add(e);
-            }
-        });
-        return intersectionSet;
-    };
-    // change code below this line
-    // change code above this line
+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;
+  }
+  // change code below this line
+  // change code above this line
 }
 ```
 
@@ -104,72 +120,89 @@ function Set() {
 <section id='solution'>
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-    // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-    // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the collection
-    this.size = function() {
-        return collection.length;
-    };
-    // this method will return the union of two sets
-    this.union = function(otherSet) {
-        var unionSet = new Set();
-        var firstSet = this.values();
-        var secondSet = otherSet.values();
-        firstSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        secondSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        return unionSet;
-    };
-    // this method will return the intersection of two sets as a new set
-    this.intersection = function(otherSet) {
-        var intersectionSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e){
-            if(otherSet.has(e)){
-                intersectionSet.add(e);
-            }
-        });
-        return intersectionSet;
-    };
-    this.difference = function(otherSet) {
-        var differenceSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e) {
-            if (!otherSet.has(e)) {
-                differenceSet.add(e);
-            }
-        });
-        return differenceSet;
+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;
+  }
 }
 ```
 
diff --git a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data.english.md b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data.english.md
index f65e2cfb79..c2ff098f24 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-subset-check-on-two-sets-of-data.english.md
@@ -43,75 +43,92 @@ tests:
 <div id='js-seed'>
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-    // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-    // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the collection
-    this.size = function() {
-        return collection.length;
-    };
-    // this method will return the union of two sets
-    this.union = function(otherSet) {
-        var unionSet = new Set();
-        var firstSet = this.values();
-        var secondSet = otherSet.values();
-        firstSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        secondSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        return unionSet;
-    };
-    // this method will return the intersection of two sets as a new set
-    this.intersection = function(otherSet) {
-        var intersectionSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e){
-            if(otherSet.has(e)){
-                intersectionSet.add(e);
-            }
-        });
-        return intersectionSet;
-    };
-    // this method will return the difference of two sets as a new set
-    this.difference = function(otherSet) {
-        var differenceSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e){
-            if(!otherSet.has(e)){
-                differenceSet.add(e);
-            }
-        });
-        return differenceSet;
-    };
-    // change code below this line
-    // change code above this line
+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
 }
 ```
 
@@ -122,7 +139,97 @@ function Set() {
 <section id='solution'>
 
 ```js
-function Set() {var collection = []; this.has = function(e){return(collection.indexOf(e) !== -1);};this.values = function() {return collection;};this.add = function(element) {if (!this.has(element)) {collection.push(element);return true;} else {return false;}};this.remove = function(element) {if(this.has(element)) {var i = collection.indexOf(element);collection.splice(i, 1);return true;}return false;};this.size = function() {return collection.length;};this.union = function(set) {var u = new Set();var c = this.values();var s = set.values();c.forEach(function(element){u.add(element);});s.forEach(function(element){u.add(element);});return u;};this.intersection = function(set) {var i = new Set();var c = this.values();c.forEach(function(element){if(s.has(element)) i.add(element);});};this.difference = function(set) {var d = new Set();var c = this.values();c.forEach(function(e){if(!set.has(e)) d.add(e);});};this.subset = function(set) {var isSubset = true;var c = this.values();c.forEach(function(e){if(!set.has(e)) isSubset = false;});return isSubset;};}
+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;
+  }
+
+  subset(set) {
+    for(const value of this.values()){
+      if(!set.dictionary[value]) return false;
+    }
+    return true
+  }
+}
 ```
 
 </section>
diff --git a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-union-on-two-sets.english.md b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-union-on-two-sets.english.md
index 273b0fdb17..f5c7f3e0c3 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-union-on-two-sets.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-a-union-on-two-sets.english.md
@@ -34,41 +34,47 @@ tests:
 <div id='js-seed'>
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-    // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-   // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the set
-    this.size = function() {
-        return collection.length;
-    };
-    // change code below this line
+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;
+    }
 
-    // change code above this line
+    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;
+  }
+  // change code below this line
+
+  // change code above this line
 }
 ```
 
@@ -79,45 +85,55 @@ function Set() {
 <section id='solution'>
 
 ```js
-function Set() {
-    var collection = [];
+class Set {
+  constructor() {
+    this.dictionary = {};
+    this.length = 0;
+  }
 
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
+  has(element) {
+    return this.dictionary[element] !== undefined;
+  }
 
-    this.values = function() {
-        return collection;
-    };
+  values() {
+    return Object.keys(this.dictionary);
+  }
 
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
+  add(element) {
+    if (!this.has(element)) {
+      this.dictionary[element] = true;
+      this.length++;
+      return true;
+    }
 
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
+    return false;
+  }
 
-    this.size = function() {
-        return collection.length;
-    };
+  remove(element) {
+    if (this.has(element)) {
+      delete this.dictionary[element];
+      this.length--;
+      return true;
+    }
 
-    this.union = function(anotherSet){
-        const newSet = new Set();
-        const addToSet = el => newSet.add(el);
-        this.values().forEach(addToSet);
-        anotherSet.values().forEach(addToSet);
-        return newSet;
-    };
+    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;
+  }
 }
 ```
 
diff --git a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-an-intersection-on-two-sets-of-data.english.md b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-an-intersection-on-two-sets-of-data.english.md
index 5c06e4ff79..1e41fc3245 100644
--- a/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-an-intersection-on-two-sets-of-data.english.md
+++ b/curriculum/challenges/english/08-coding-interview-prep/data-structures/perform-an-intersection-on-two-sets-of-data.english.md
@@ -35,53 +35,58 @@ tests:
 <div id='js-seed'>
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-   // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-    // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the collection
-    this.size = function() {
-        return collection.length;
-    };
-    // this method will return the union of two sets
-    this.union = function(otherSet) {
-        var unionSet = new Set();
-        var firstSet = this.values();
-        var secondSet = otherSet.values();
-        firstSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        secondSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        return unionSet;
-    };
-    // change code below this line
-    // change code above this line
+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;
+  }
+  // change code below this line
+  // change code above this line
 }
 ```
 
@@ -93,61 +98,77 @@ function Set() {
 
 
 ```js
-function Set() {
-    // the var collection will hold the set
-    var collection = [];
-    // this method will check for the presence of an element and return true or false
-    this.has = function(element) {
-        return (collection.indexOf(element) !== -1);
-    };
-    // this method will return all the values in the set
-    this.values = function() {
-        return collection;
-    };
-   // this method will add an element to the set
-    this.add = function(element) {
-        if(!this.has(element)){
-            collection.push(element);
-            return true;
-        }
-        return false;
-    };
-    // this method will remove an element from a set
-    this.remove = function(element) {
-        if(this.has(element)){
-           var index = collection.indexOf(element);
-            collection.splice(index,1);
-            return true;
-        }
-        return false;
-    };
-    // this method will return the size of the collection
-    this.size = function() {
-        return collection.length;
-    };
-    // this method will return the union of two sets
-    this.union = function(otherSet) {
-        var unionSet = new Set();
-        var firstSet = this.values();
-        var secondSet = otherSet.values();
-        firstSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        secondSet.forEach(function(e){
-            unionSet.add(e);
-        });
-        return unionSet;
-    };
-    this.intersection = function(otherSet) {
-        var intersectionSet = new Set();
-        var firstSet = this.values();
-        firstSet.forEach(function(e) {
-            if (otherSet.has(e)) {
-                intersectionSet.add(e);
-            }
-        })
-        return intersectionSet;
+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;
+  }
 }
 ```