For loop with index (withIndex) in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the withIndex() function do in a Kotlin for loop?

It allows you to loop over a collection while accessing both the index and the value of each element at the same time.

beginner

How do you access the index and value inside a for loop using withIndex()?

You can use destructuring syntax: for ((index, value) in collection.withIndex()) where index is the position and value is the element.

intermediate

Why is using withIndex() better than manually managing an index variable in a loop?

Because it is cleaner, less error-prone, and Kotlin handles the index automatically, so you don’t have to update it yourself.

beginner

Write a simple Kotlin for loop using withIndex() to print each index and value from a list of fruits.

Example:<br>val fruits = listOf("Apple", "Banana", "Cherry")<br>for ((index, fruit) in fruits.withIndex()) {<br> println("Fruit at index $index is $fruit")<br>}

beginner

Can withIndex() be used with arrays and other collections in Kotlin?

Yes, withIndex() works with arrays, lists, and any iterable collection to provide index-value pairs.

What does withIndex() return when called on a list?

A Only the values of the list

B Only the indexes of the list

C A sequence of index-value pairs

D A reversed list

withIndex() returns a sequence of pairs where each pair contains the index and the corresponding value from the list.

How do you write a for loop to get both index and value from a list items?

A for (item in items.withIndex())

B for ((index, item) in items.withIndex())

C for (index, item in items)

D for (index in items)

Option B uses destructuring to get both index and value from withIndex().

Which of these is a benefit of using withIndex() in Kotlin loops?

A It filters out null values

B It automatically sorts the list

C It converts the list to a map

D It provides both index and value without manual index tracking

withIndex() helps you get index and value easily without managing an index variable yourself.

What happens if you use for (index in list.withIndex()) without destructuring?

A You get a pair object containing index and value

B You get the index only

C You get the value only

D You get a compile error

Without destructuring, the loop variable is a pair containing both index and value.

Can withIndex() be used with arrays in Kotlin?

A Yes, arrays and other iterable collections

B Only with maps

C No, only lists

D Only with strings

withIndex() works with arrays, lists, and other iterable collections.

Explain how to use withIndex() in a Kotlin for loop to access both index and value.

Think about how you get both position and element in the loop.

Why is using withIndex() preferred over manually incrementing an index variable in loops?

Consider what problems manual index management can cause.