Map transformation in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a Map transformation in Kotlin?

A Map transformation in Kotlin means creating a new Map by changing the keys, values, or both from an existing Map without modifying the original one.

beginner

How do you transform only the values of a Map in Kotlin?

You use the mapValues function, which applies a transformation to each value while keeping the keys the same.

beginner

What does the mapKeys function do in Kotlin?

The mapKeys function creates a new Map by transforming the keys of the original Map while keeping the values unchanged.

beginner

Show a simple example of transforming a Map's values by doubling them.

Given val map = mapOf("a" to 1, "b" to 2), <br> val doubled = map.mapValues { it.value * 2 } <br> Result: {"a"=2, "b"=4}

intermediate

Can you transform both keys and values of a Map at the same time in Kotlin?

Yes, by using the map function on the Map's entries and then converting the result back to a Map with toMap().

Which Kotlin function transforms only the values of a Map?

A mapKeys

B mapValues

C map

D filter

The mapValues function changes only the values, keeping keys the same.

What does mapKeys do?

A Filters keys

B Transforms values only

C Transforms both keys and values

D Transforms keys only

mapKeys changes keys but keeps values unchanged.

How do you transform both keys and values of a Map?

A Use mapValues and mapKeys together

B Use filter

C Use map on entries and then toMap()

D Use reduce

Using map on entries lets you change both keys and values, then toMap() converts back to a Map.

What is the result of mapOf("x" to 3).mapValues { it.value + 1 }?

A {"x"=4}

B {"x"=3}

C {"x"=1}

D {}

The value 3 is increased by 1, resulting in 4.

Which function keeps the original Map unchanged and returns a new transformed Map?

A Both A and C

B mapValues

C mapKeys

D None

Both mapValues and mapKeys return new Maps without changing the original.

Explain how to transform only the values of a Map in Kotlin and give a simple example.

Think about a function that changes values but keeps keys the same.

Describe how to transform both keys and values of a Map in Kotlin.

Use map on entries and then convert back to Map.