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

madkrell

6 minutes ago

4.90ms

89.23kb

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

wassie1256

5 hours ago

4.95ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    for num in slice.iter_mut() {
        if *num % 2 == 0 {
            *num *= 2;  // Double even numbers
        } else {
            *num -= 1;  // Subtract 1 from odd numbers
        }
    }
}
// Example Usage
fn main() {
    let mut numbers = [1, 2, 3, 4, 5];
    transform_even_odd(&mut numbers);
    assert_eq!(numbers, [0, 4, 2, 8, 4]);  // Expected result after transformation
    let mut empty: [i32; 0] = [];
    transform_even_odd(&mut empty);
    assert_eq!(empty, []);  // No changes
    println!("All tests passed!");
}

Elizabeth Doughty

Thymelizabeth

6 hours ago

4.43ms

89.23kb

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

Elizabeth Doughty

Thymelizabeth

6 hours ago

5.44ms

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; });
}

Esteban Pérez

lep511

7 hours 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 x in slice.iter_mut() {
        if *x % 2 == 0 {
            *x *= 2;
        } else {
            *x -= 1;
        }
    }
}

Esteban Pérez

lep511

7 hours ago

7.13ms

89.23kb

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

kustrun

8 hours ago

3.76ms

89.23kb

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

YCH931

a day ago

4.40ms

89.23kb

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

Max

maxemontio

a day ago

5.09ms

89.23kb

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

Lucas Deprit

lucasdeprit

a day ago

4.89ms

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 == 0 { *i = 0 }
        if *i % 2 == 0 {
            *i *= 2;
        } else {
            *i -= 1;
        }
    }
}

jordan-betterman

2 days ago

5.56ms

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 = *i*2;
        }
        else {
            *i = *i-1;
        }
    }
}

Facundo Hernandez

facuhernandez99

2 days ago

10.11ms

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;
        }
    }
}

G Towers

gtowers-dukosi

2 days ago

4.40ms

89.23kb

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

Hung Dinh

nhdinh

3 days ago

4.44ms

89.23kb

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

Hung Dinh

nhdinh

3 days ago

6.50ms

89.23kb

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

Nelly

nellyisanon

3 days ago

8.64ms

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 {
        if *i % 2 == 0 {
            *i *= 2;
        }
        else {
            *i -= 1;
        }
    }
}

Likith-LVSHD

3 days ago

5.67ms

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{
        if *i%2==0{
            *i *=2;
        }
        else{
            *i -=1;
        }
    }
}

Madhankumar Anandan

amkumar072

3 days ago

4.19ms

89.23kb

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

amaneru

7ma8no9

3 days ago

5.08ms

89.23kb

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

Pranav Garg

PranavGarg01

4 days ago

4.27ms

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 {
        if *i%2 == 0 {
            *i *=2;
        }
        else {
            *i -=1;
        }
    }
}

Artyom Chebotarev

Derik117

5 days ago

4.14ms

89.23kb

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

Heatiche Mix

HeaticheTakachi

6 days ago

4.82ms

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;
        }
    }
}

zawwwu

6 days ago

4.79ms

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});
}

zawwwu

6 days ago

4.15ms

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});
}

AKA.MoneyTaker

M4Bo2

7 days ago

5.60ms

89.23kb

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

SilentCanon

silentcanon

7 days ago

4.30ms

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 = *i * 2;
        } else {
            *i = *i - 1
        }
    }
}

AnKarl

Zythophilus

7 days ago

3.88ms

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
        }
    }
}

pagyeman

7 days ago

8.01ms

89.23kb

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

JackY

Scorpio24

8 days ago

5.02ms

89.23kb

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

Éric Villani

TheTrueCaligari

9 days ago

6.56ms

89.23kb

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

Lê Minh Quân

aleister1102

9 days ago

4.63ms

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

Lê Minh Quân

aleister1102

9 days ago

4.81ms

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

Lê Minh Quân

aleister1102

9 days ago

10.64ms

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;
        }
    }
}

Yi Hao

leongyihao

10 days ago

4.05ms

89.23kb

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

fyroostr

10 days ago

3.75ms

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 {
        match item {
            item if *item%2 == 0 => *item *= 2,
            item if *item%2 != 0 => *item -= 1,
            _ => {}
        }
    }
}

fyroostr

10 days ago

4.97ms

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() {
        match item {
            item if *item%2 == 0 => *item *= 2,
            item if *item%2 != 0 => *item -= 1,
            _ => {}
        }
    }
}

EduardoFernandess

11 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.
    for item in slice {
        if *item % 2 == 0 {
            *item *= 2;
        } else {
            *item -= 1;
        }
    }
}

PixelForg

11 days ago

7.91ms

89.23kb

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

ahmedzghal

11 days ago

4.31ms

89.23kb

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

MESTRE Sylvain

Shult

11 days ago

5.14ms

89.23kb

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

Muhammad Najib Bala

NAJIB-B

11 days ago

8.08ms

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
        }
    }
}

Tomaz Azinhal

tomazinhal

11 days ago

4.87ms

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 = *value * 2;
        }
        else {
            *value = *value - 1;
        }
    }
}

Andrew Nicholls

Booleans

12 days ago

9.01ms

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;
        }
    }
}

Ayushman Rathore

Spartan09

12 days ago

5.13ms

89.23kb

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

Rafik

RafikGadzhiyev

12 days ago

4.22ms

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
        }
    }
}

Deaddy3

12 days ago

6.80ms

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;
        }
    }
}

Dyaa Adel

dyaa-adel

13 days ago

3.89ms

89.23kb

pub fn transform_even_odd(slice: &mut [i32]) {
    // Your code here: iterate over the mutable slice and modify its elements.
    for v in slice.iter_mut() {
        if (*v & 0b1) > 0 { // ODd
            *v -= 1;
        } else { // even
            *v *= 2;
        }
    }
}

Alberto Nidasio

NidasioAlberto

13 days ago

4.10ms

89.23kb

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

Anıl Şenay

anilsenay

13 days ago

4.93ms

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(|x| {
        if *x % 2 == 0 {
            *x = *x * 2
        } else {
            *x = *x - 1
        }
    });}

Evan

0xIchigo

13 days ago

4.79ms

89.23kb

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