rustLogic errorMedium

Indexing fails on preallocated but empty Rust vector

Time: 0:00

BugFind the bug and fix the code

What it should do

Initialize a vector with a given capacity and set the first element. Example: initialize_vector(5, 10) -> [10, 0, 0, 0, 0]

What happens instead

thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', src/main.rs:6:18

fn initialize_vector(capacity: usize, value: i32) -> Vec<i32> {
    let mut vec = Vec::with_capacity(capacity);
    vec[0] = value;
    vec
}

fn main() {
    let vec = initialize_vector(5, 10);
    println!("{:?}", vec);
}

Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).

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Hints

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Hint 3

Unlocks after Hint 2

This bug belongs to the logic errors pattern

The wrong operator, an inverted condition, a formula the right way round but backwards.

Learn the logic errors pattern Step through your own code

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fn initialize_vector(capacity: usize, value: i32) -> Vec<i32> { let mut vec = Vec::with_capacity(capacity); vec[0] = value; vec } fn main() { let vec = initialize_vector(5, 10); println!("{:?}", vec); }

Indexing fails on preallocated but empty Rust vector

What it should do

What happens instead

More logic errors to practise

Indexing fails on preallocated but empty Rust vector

What it should do

What happens instead

More logic errors to practise