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:

1. Double each even number in the slice.
2. Subtract 1 from each odd number in the slice.
3. 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:

<details> <summary>Additional Hints</summary>

• 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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