Rust Iterators Quiz

Rust

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Master Rust's powerful iterator system for efficient data processing and transformation

40 Questions

~80 minutes

Question 1

What is the Iterator trait in Rust?

A trait that defines how to iterate over a sequence of values

A trait for creating loops

A trait for collections

A trait for functions

Question 2

What is the signature of the next() method in Iterator?

fn next(&mut self) -> Option<Self::Item>

fn next(&self) -> Option<Self::Item>

fn next(&mut self) -> Self::Item

fn next() -> Option<Self::Item>

Question 3

What does this iterator code produce?

rust

let v = vec![1, 2, 3];
let mut iter = v.iter();
println!("{:?}", iter.next());
println!("{:?}", iter.next());

Some(1) Some(2)

Some(&1) Some(&2)

1 2

Compilation error

Question 4

What is the difference between iter() and into_iter()?

iter() borrows elements, into_iter() takes ownership

iter() takes ownership, into_iter() borrows

They are identical

into_iter() doesn't exist

Question 5

What are iterator adapters?

Methods that transform one iterator into another

Methods that consume iterators

Methods that create iterators

Iterator adapters don't exist

Question 6

What does the map() adapter do?

Transforms each element using a closure

Filters elements based on a condition

Collects elements into a collection

Finds the first matching element

Question 7

What does this map() example produce?

rust

let v = vec![1, 2, 3];
let doubled: Vec<i32> = v.iter().map(|x| x * 2).collect();

[2, 4, 6]

[1, 2, 3]

Compilation error

Runtime error

Question 8

What does the filter() adapter do?

Keeps only elements that match a predicate

Transforms elements

Sorts elements

Removes duplicates

Question 9

What does this filter() example produce?

rust

let v = vec![1, 2, 3, 4, 5];
let even: Vec<i32> = v.into_iter().filter(|x| x % 2 == 0).collect();

[2, 4]

[1, 3, 5]

[1, 2, 3, 4, 5]

[]

Question 10

What are iterator consumers?

Methods that consume the iterator and return a final value

Methods that create iterators

Methods that transform iterators

Iterator consumers don't exist

Question 11

What does the collect() consumer do?

Transforms an iterator into a collection

Sums all elements

Counts elements

Finds maximum value

Question 12

What does this collect() example do?

rust

let v = vec![1, 2, 3];
let doubled: Vec<i32> = v.iter().map(|&x| x * 2).collect();

Creates [2, 4, 6] by dereferencing and doubling

Compilation error due to wrong dereference

Creates [1, 2, 3]

Runtime error

Question 13

What does the sum() consumer do?

Adds all elements together

Multiplies all elements

Finds the average

Counts elements

Question 14

What does this sum() example produce?

rust

let v = vec![1, 2, 3, 4];
let total: i32 = v.iter().sum();

Compilation error

Runtime error

Question 15

What does the count() consumer do?

Returns the number of elements in the iterator

Returns the sum of elements

Returns the first element

Returns the last element

Question 16

What is lazy evaluation in iterators?

Operations are performed only when the result is needed

Operations are performed immediately

Operations are cached

Lazy evaluation doesn't apply to iterators

Question 17

What happens in this lazy evaluation example?

rust

let v = vec![1, 2, 3, 4, 5];
let result: Vec<i32> = v.iter()
    .map(|x| {
        println!("Mapping {}", x);
        x * 2
    })
    .filter(|x| {
        println!("Filtering {}", x);
        x > &4
    })
    .collect();

Prints occur only when collect() is called, showing lazy evaluation

Prints occur immediately for all elements

No prints occur

Compilation error

Question 18

How do you create a custom iterator?

Implement the Iterator trait with next() method

Use a for loop

Use collect()

Custom iterators are not possible

Question 19

What is required to implement a custom iterator?

Implement Iterator trait with Item associated type and next() method

Just implement next() method

Implement IntoIterator trait

No implementation needed

Question 20

What does this custom iterator example do?

rust

struct Counter {
    count: u32,
}

impl Iterator for Counter {
    type Item = u32;
    
    fn next(&mut self) -> Option<Self::Item> {
        self.count += 1;
        if self.count < 6 {
            Some(self.count)
        } else {
            None
        }
    }
}

Creates an iterator that yields 1, 2, 3, 4, 5

Creates an iterator that yields 0, 1, 2, 3, 4

Compilation error

Infinite iterator

Question 21

What is the IntoIterator trait?

Trait that defines how to convert a type into an iterator

Trait for creating iterators

Trait for consuming iterators

IntoIterator doesn't exist

Question 22

What is the difference between Iterator and IntoIterator?

IntoIterator converts types to iterators, Iterator defines iteration behavior

They are the same trait

Iterator converts types, IntoIterator defines behavior

Neither trait exists

Question 23

What does the enumerate() adapter do?

Adds an index to each element, returning (index, element) pairs

Numbers elements starting from 1

Counts total elements

Enumerate doesn't exist

Question 24

What does this enumerate() example produce?

rust

let v = vec!['a', 'b', 'c'];
let enumerated: Vec<(usize, char)> = v.iter().enumerate().collect();

[(0, 'a'), (1, 'b'), (2, 'c')]

[(1, 'a'), (2, 'b'), (3, 'c')]

['a', 'b', 'c']

Compilation error

Question 25

What does the zip() adapter do?

Combines two iterators into pairs

Compresses elements

Skips elements

Zip doesn't exist

Question 26

What does this zip() example produce?

rust

let a = vec![1, 2, 3];
let b = vec!['a', 'b'];
let zipped: Vec<(i32, char)> = a.iter().zip(b.iter()).collect();

[(1, 'a'), (2, 'b')]

[(1, 'a'), (2, 'b'), (3, ?)]

Compilation error

[(1, 'a'), (2, 'b'), (3, 'c')]

Question 27

What does the take() adapter do?

Takes the first n elements from an iterator

Takes all elements

Takes the last n elements

Take doesn't exist

Question 28

What does the skip() adapter do?

Skips the first n elements and yields the rest

Skips all elements

Skips every nth element

Skip doesn't exist

Question 29

What does the chain() adapter do?

Combines two iterators into one continuous iterator

Chains function calls

Creates a linked list

Chain doesn't exist

Question 30

What does this chain() example produce?

rust

let a = vec![1, 2];
let b = vec![3, 4];
let chained: Vec<i32> = a.iter().chain(b.iter()).collect();

[1, 2, 3, 4]

[3, 4, 1, 2]

[[1, 2], [3, 4]]

Compilation error

Question 31

What does the fold() consumer do?

Accumulates values using a closure that takes accumulator and element

Folds elements into a single value

Creates multiple values

Fold doesn't exist

Question 32

What does this fold() example produce?

rust

let v = vec![1, 2, 3, 4];
let sum = v.iter().fold(0, |acc, x| acc + x);

Compilation error

Question 33

What does the any() consumer do?

Returns true if any element matches the predicate

Returns true if all elements match

Returns the first matching element

Any doesn't exist

Question 34

What does the all() consumer do?

Returns true if all elements match the predicate

Returns true if any element matches

Returns all matching elements

All doesn't exist

Question 35

What does the find() consumer do?

Returns the first element that matches the predicate

Returns all matching elements

Returns the index of matching element

Find doesn't exist

Question 36

What is iterator performance like compared to loops?

Iterators can be as fast as loops due to optimization

Iterators are always slower than loops

Loops are always slower than iterators

Performance depends on usage

Question 37

What is the advantage of lazy evaluation?

Avoids unnecessary computation and enables short-circuiting

Makes code run faster

Uses less memory

Lazy evaluation has no advantages

Question 38

How do you implement IntoIterator for a custom type?

Implement IntoIterator trait with into_iter() method

Implement Iterator trait

Use a macro

IntoIterator cannot be implemented

Question 39

What is the difference between iter() and iter_mut()?

iter() borrows immutably, iter_mut() borrows mutably

iter() takes ownership, iter_mut() borrows

They are identical

iter_mut() doesn't exist

Question 40

In a data processing pipeline where you need to filter a large dataset, transform each element, and collect only the first 10 results, which iterator approach would be most efficient and why?

Use filter().map().take(10).collect() for lazy evaluation and early termination

Collect first, then filter/map/take to process all data unnecessarily

Use loops with break for manual control

Process all data and slice the result

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Rust Iterators Quiz

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18

Question 19

Question 20

Question 21

Question 22

Question 23

Question 24

Question 25

Question 26

Question 27

Question 28

Question 29

Question 30

Question 31

Question 32

Question 33

Question 34

Question 35

Question 36

Question 37

Question 38

Question 39

Question 40

What Are Iterators in Rust?

What You Will Practise

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Generic

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Concurrency

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Crate Architecture

Performance and Optimization