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Ivy-Walobwa
Ivy-Walobwa

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Set Algorithms

#javascript #webdev #computerscience

A set is a collection of any type of comparable data. Data in a set can occur only once.
Example;

{..., -3, -1, 1, 3, ...} is a set of odd numbers
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Basic Set Implementations

new Set() - create a new set
Set.prototype.has() - returns true if element is present in Set object
Set.prototype.add() - adds a new item to set object
Set.prototype.delete() - removes specified item from set object

1.Union Algorithm
This is a set algorithm that compares two sets and returns a third set that contains all of the unique items in both sets.

 function union(setA, setB) { let result = new Set(setA); // new set containing items in setA for (let elem of setB) { // add items from setB to the new set // an element can't be added twice result.add(elem); } return result; } let setA = new Set([1, 2, 3]); let setB = new Set([3, 4, 5]); console.log(union(setA, setB)); // >> Set { 1, 2, 3, 4, 5 }
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2.Intersection Algorithm
Compares two sets and returns a third set that contains all of the matching members of both sets.

function intersection(setA, setB) { let result = new Set(); // new empty set for (let elem of setA) { if (setB.has(elem)){ // if matching elements found result.add(elem); // add to new set } } return result; } let setA = new Set([1, 2, 3]); let setB = new Set([2, 3, 4]); console.log(intersection(setA, setB)); // >> Set { 2, 3 }
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3.Set Difference Algorithm
Takes two sets, A and B, and return all the items of A that are not members of B.

function setDifference(setA, setB) { let result = new Set(setA); for (let item of setB) { result.delete(item); // delete items in A that exist in B } return result; } let setA = new Set([2, 3, 4]); let setB = new Set([3, 4, 5]); console.log(setDifference(setA, setB)); // >> Set { 2 }
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4.Symmetric Difference Algorithm
Takes two sets and returns a third set that contains all of the members of both sets that are not in the other

function symmetricDifference(setA, setB) { let difference = new Set(setA); for (let elem of setB) { if (difference.has(elem)) { difference.delete(elem); // if item in B exists in A, remove } else { difference.add(elem) // else add to new set } } return difference; } let setA = new Set([1, 2, 3]); let setB = new Set([2, 3, 4]); console.log(symmetricDifference(setA, setB)); // >> Set { 1, 4 }
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Symmetric Difference can also be described as the set difference of the intersection and union of the input sets

function symmetricDifference(setA, setB) { let intersectionResult = intersection(setA, setB) let unionResult = union(setA, setB); return setDifference(unionResult, intersectionResult,) } let setA = new Set([1, 2, 3]); let setB = new Set([2, 3, 4]); console.log(symmetricDifference(setA, setB)); // >> Set { 1, 4 }
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Reference

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