Mutable Slices

In this challenge, you'll explore how to work with mutable slices in Rust. A mutable slice, &mut [T], allows you to modify the elements of a collection directly and efficiently without creating a new collection.

Slices are a fundamental part of Rust, providing a view into contiguous sequences of elements such as arrays or vectors. When working with slices, you can iterate over and manipulate the elements dynamically.

Your Task

Write a function modify_elements(slice: &mut [i32]) that modifies the elements of a mutable slice of integers in the following way:

Double each even number in the slice.
Subtract 1 from each odd number in the slice.
Modify the elements directly without creating a new collection.

Example

let mut numbers = [1, 2, 3, 4, 5];
modify_elements(&mut numbers);
 
// Odd numbers reduced by 1
// Even numbers doubled
assert_eq!(numbers, [0, 4, 2, 8, 4]);
 
let mut numbers = [10, 15, 20];
modify_elements(&mut numbers);
 
// 10 -> 20, 15 -> 14, 20 -> 40
assert_eq!(numbers, [20, 14, 40]);

Hints

If you're stuck, here are some hints to help you:

Additional Hints

Use the .iter_mut() method to traverse the slice by mutable reference.
Remember that you can check if a number is even using num % 2 == 0.
Use dereferencing (*) to update the value pointed to by the mutable reference.
You can use a for loop with mutable references for concise modification.
The slice directly modifies the original collection it is derived from, so no need to return anything.

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Solutions

Chih Ying Yen

xavierforge

2 hours ago

4.12ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut() { 
        if *num % 2 == 0 {
            *num *= 2;
        } else {
            *num -= 1;
        }
    }
}

Dominik P

ddominikp

17 hours ago

3.98ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for el in slice {
        if *el % 2 == 0 {
            *el *= 2;
        } else {
            *el -= 1;
        }
    }
    ()
}

Noxyss

20 hours ago

6.39ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for element in slice {
        if (*element % 2) == 0 {
            *element *= 2
        } else {
            *element -= 1
        }
    }
}

Harsh Ranjan

harshRn

21 hours ago

4.01ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|e| {if *e % 2 == 0 { *e *= 2;} else { *e -= 1; }});
}

bernardoLY19

2 days ago

4.39ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in slice.iter_mut() {
        if *i%2 == 0 {
            *i = 2 * *i;
        } else {
            *i = *i - 1;
        }
    }
}

HAYASAKA Ryosuke

HAYASAKA-Ryosuke

2 days ago

4.29ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|v| {
        if *v % 2 == 0 {
            *v *= 2;
        }else{
            *v -= 1;
        }
    })
}

oliverer3

3 days ago

4.71ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    let slice_iter = slice.iter_mut();
    for num in slice_iter {
        if *num % 2 == 0 {
            *num = *num * 2;
        }else{
            *num = *num - 1;
        }
    }
}

Shu

AlbedoAi

3 days ago

3.93ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for n in slice.iter_mut() {
        if *n % 2 == 0 {
            *n *= 2;
        }
        else {
            *n -= 1;
        }
    }
}

Baron Curtin

baroncurtin2

3 days ago

3.90ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(mutate_number)
}
fn mutate_number(n: &mut i32) {
    if *n % 2 == 0 {
        *n *= 2;
    } else {
        *n -= 1;
    }
}

yaniel-dr

4 days ago

3.98ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|val| {
        *val = if *val % 2 == 0 {
            *val * 2
        }
        else {
            *val - 1
        }
    })
}

Cobran53

4 days ago

4.13ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in slice.iter_mut() {
        *i = if *i%2 == 0 {*i*2} else {*i-1}
    }
}

razabc

4 days ago

4.08ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // // Your code here: iterate over the mutable slice and modify its elements.
    for element in slice.iter_mut() {
        *element = if *element % 2 == 0 {*element*2} else {*element - 1};
    }
}

Hrithz2

4 days ago

4.04ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut(){
        if *num % 2 == 0{
            *num *= 2;
        }
        else{
            *num -= 1;
        }
    }
}

xvzhang

xvzhnang

5 days ago

4.03ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in slice.iter_mut() {
        if *i % 2 == 0 {
            *i *= 2
        } else {
            *i -= 1
        }
    }
}

Gerasimos

glomvardos

6 days ago

4.03ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut() {
         if *num % 2 == 0 {
            *num *= 2;
            continue;
         }
         *num -= 1;
    }
}

alexsavio

7 days ago

3.96ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut() {
        if *num % 2 == 0 {
            *num *= 2;
        }
        else {
            *num -= 1;
        }
    }
}

Raj

irajgill

7 days ago

4.02ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in 0..slice.len(){
        if slice[i] % 2 == 0 {
            slice[i] *= 2
        }
        else {
            slice[i] -= 1
        }
    }
}

Javets70

7 days ago

4.45ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in 0..slice.len(){
        if slice[i] % 2 == 0{
            slice[i] *= 2
        } else {
            slice[i] -= 1
        }
    }
}

Javets70

7 days ago

4.21ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in 0..slice.len(){
        if slice[i] % 2 == 0{
            slice[i] *= 2
        } else {
            slice[i] -= 1
        }
    }
}

Herman effendi

hrmneffdii

9 days ago

5.35ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for number in slice.iter_mut(){
        if *number % 2 == 0 {
            *number = *number * 2;
        }else {
            *number = *number - 1;
        }
    }
}

Krishnan Raj Luhar

luharkri

9 days ago

6.23ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut(){
        if *num % 2 == 0{
            *num *= 2
        }
        else {
            *num -= 1
        }
    }
}

cortexiphan

9 days ago

4.52ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for it in slice.iter_mut() {
        if *it % 2 == 0 {
            *it *= 2
        } else {
            *it -= 1
        }
    }
}

Alex C

Alextibtab

9 days ago

4.49ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    if slice.is_empty() { () }
    for num in slice.iter_mut() {
        if *num % 2 == 0 {
            *num *= 2;
        }
        else {
            *num -= 1;
        }
    }
}

Artem Nistuley

artemnistuley

9 days ago

4.62ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for item in slice.iter_mut() {
        if *item % 2 == 0 {
            *item = *item * 2;
        } else {
            *item = *item - 1;
        }
    }
}

Jai

jsat97

10 days ago

4.69ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|i| if *i%2 == 0 {*i *=2; } else {*i -= 1;});
}

Taeyoon Kim

partrita

10 days ago

4.15ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut() {
        if *num == 0 {
            // leave zero as zero
        } else if *num % 2 == 0 {
            *num *= 2;   // double non-zero evens
        } else {
            *num -= 1;   // subtract one from odds
        }
    }
}

Miguel Ángel Allende

maallende

11 days ago

4.75ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in slice.iter_mut(){
        if *i % 2 == 0 {
            *i *= 2; // Double the value if it's even
        } else {
            *i -= 1; // Increment the value if it's odd
        }
    }
}

coreyralph

11 days ago

4.26ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    slice.iter_mut().for_each(|i|
        if *i % 2 == 0 {
            *i *= 2
        } else {
            *i -= 1
        }
    );
}

coreyralph

11 days ago

4.28ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    slice.iter_mut().for_each(|i|
        if *i % 2 == 0 {
            *i *= 2
        } else {
            *i -= 1
        }
    );
}

CDzungx

11 days ago

3.80ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut() {
        if *num % 2==0 {*num*=2;} 
        else {*num-=1;}
    }
}

Philippe Massicotte

PMassicotte

12 days ago

4.06ms

89.23kb

fn is_even(n: &mut i32) -> bool {
    *n % 2 == 0
}
pub fn transform_even_odd(slice: &mut [i32]) {
    slice.iter_mut().for_each(|n| {
        *n = match is_even(n) {
            true => *n * 2,
            false => *n - 1,
        };
    });
}

Saverio Brancaccio

savbran

12 days ago

4.24ms

91.21kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    println!("num_slice: {:?}", slice);
    for n in slice.iter_mut() {
        if *n % 2 == 0 { *n *= 2 }
        else { *n -= 1 }
    };
    println!("transfomed num_slice: {:?}", slice);
}

Saverio Brancaccio

savbran

12 days ago

8.22ms

91.21kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    println!("num_slice: {:?}", slice);
    for n in slice.iter_mut() {
        if *n % 2 == 0 { *n *= 2 }
        else { *n -= 1 }
    };
    println!("transfomed num_slice: {:?}", slice);
}

Jatin

jatinpatel05

12 days ago

4.11ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice.iter_mut(){
        if *num % 2 == 0 {
            *num = *num * 2;
        }
        else {
            *num = *num -1 ;
        }
    }
}

Regulus-Sun

13 days ago

5.05ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for num in slice.iter_mut() {
        if *num % 2 == 0 {
            *num *= 2;
        } else {
            *num -= 1;
        }
    }
}

LouisMareschal

13 days ago

3.94ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for val_mut in slice.iter_mut(){
        if *val_mut % 2 == 0 {
            *val_mut *= 2;
        } else{
            *val_mut -= 1;
        }
    } 
}

Luigi Terrone

LuigiTer

14 days ago

4.75ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for val in slice.iter_mut() {
        if *val % 2 == 0 {
            *val *= 2; 
        }
        else {
            *val -= 1; 
        }
        
    }
}

KuuShyn

15 days ago

4.76ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for num in slice {
        if *num % 2 == 0 {
            *num *= 2;
        }
        else {
            *num -= 1;
        }
    }
}

Moloson

15 days ago

4.34ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for x in slice.iter_mut(){
        if *x%2 == 0 {
            *x *= 2
        }else{
            *x -= 1
        }
    }
}

Oleksandr Vechirko

alexvechirko

15 days ago

4.40ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for i in slice.iter_mut() {
        if *i % 2 == 0 {
            *i *= 2;
        } else {
            *i -= 1;
        }
    }
}

Heino Mortensen

hmortensen83

15 days ago

5.63ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for i in slice {
        if *i % 2 == 0 {
            *i *= 2;
        } else {
            *i -= 1;
        }
    }
}

Karol Płatkowski

spoohie

16 days ago

6.03ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for element in slice.iter_mut() {
        if *element % 2 == 0 {
            *element *= 2;
        } else {
            *element -= 1;
        }
    }
}

Camiam144

16 days ago

4.71ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for elem in slice {
        if *elem % 2 == 0 {
             *elem *= 2;
        }
        else {
            *elem -= 1;
        }
    }
}

Camiam144

16 days ago

4.96ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for elem in slice.iter_mut() {
        if *elem % 2 == 0 {
             *elem *= 2;
        }
        else {
            *elem -= 1;
        }
    }
}

IwantHAPPINESS

16 days ago

5.64ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|e| {
        if *e % 2 == 0 {
            *e *= 2;
        } else {
            *e -= 1;
        }
    });
}

IwantHAPPINESS

16 days ago

4.49ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    slice.iter_mut().for_each(|e| {
        if *e % 2 == 0 {
            *e *= 2;
        } else {
            *e -= 1;
        }
    });
}

ydiarra

17 days ago

6.17ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for i in slice.iter_mut(){
        match *i{
            n if (*i)%2 ==0 => *i = n*2,
            n => *i = n-1,
        }
    }
}

0x0f1

Paul4673

17 days ago

4.64ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for element in slice {
        if *element % 2 == 0 {
            *element *= 2;
        } else {
            *element -= 1;
        }
    }
}

0x0f1

Paul4673

17 days ago

4.18ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for element in slice {
        if *element % 2 == 0 {
            *element *= 2;
        } else {
            *element -= 1;
        }
    }
}

dattruongdev

18 days ago

4.23ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for value in slice {
        if *value % 2 == 0 {
            *value *= 2;
        } else {
            *value -= 1;
        }
    }
}