Set algebra (union, intersection, difference) in Swift - Cheat Sheet & Quick Revision

Recall & Review

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What is the union of two sets in Swift?

The union of two sets is a new set containing all unique elements from both sets combined.

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How do you find the intersection of two sets in Swift?

The intersection of two sets is a new set containing only the elements that appear in both sets.

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What does the difference of two sets represent?

The difference of two sets is a new set containing elements that are in the first set but not in the second set.

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Swift code: What does this do? <br><pre>let a: Set&lt;Int&gt; = [1, 2, 3]<br>let b: Set&lt;Int&gt; = [3, 4, 5]<br>let result = a.union(b)</pre>

It creates a new set with all unique elements from sets a and b: {1, 2, 3, 4, 5}.

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Swift code: What is the result of this? <br><pre>let a: Set&lt;Int&gt; = [1, 2, 3, 4]<br>let b: Set&lt;Int&gt; = [3, 4, 5]<br>let result = a.subtracting(b)</pre>

It creates a new set with elements in a but not in b: {1, 2}.

Which Swift method returns elements common to both sets?

A union()

B subtracting()

C intersection()

D adding()

The intersection() method returns elements that appear in both sets.

What does the union() method do in Swift sets?

A Returns elements only in the first set

B Returns all unique elements from both sets

C Returns elements only in the second set

D Removes elements from the first set

union() combines all unique elements from both sets.

If you want elements in set A but not in set B, which method do you use?

A symmetricDifference()

B intersection()

C union()

D subtracting()

subtracting() returns elements in the first set that are not in the second.

What is the result of Set([1, 2, 3]).intersection(Set([3, 4, 5])) in Swift?

A {3}

B {1, 2}

C {4, 5}

D {1, 2, 3, 4, 5}

Only 3 is common to both sets.

Which method would you use to find elements in either set but not in both?

A symmetricDifference()

B intersection()

C subtracting()

D union()

symmetricDifference() returns elements in either set but not in both.

Explain how to use union, intersection, and difference with Swift sets.

Think about combining, overlapping, and excluding elements.

Describe a real-life example where set difference is useful.

Imagine two lists and what is unique to one.