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Iterators are a powerful abstraction in Rust, enabling developers to process sequences of data in a functional, efficient, and composable way. They are the foundation of many collection-related operations and provide a clean and expressive alternative to traditional loops.

In this challenge, you will implement two functions that utilize iterators to perform specific operations:

  1. Filtering out even numbers from a sequence of integers.
  2. Converting strings to uppercase from a sequence of string slices.

Using Rust's iterator methods such as filter, map, and collect, you'll create concise, functional implementations that demonstrate the elegance and power of iterators.

Your Task

Write the following two functions:

  1. filter_even_numbers:
    Takes an iterator of integers and filters out even numbers, returning a vector of the remaining odd numbers.

  2. uppercase_strings:
    Takes an iterator of string slices and converts each string to uppercase, returning a vector of the transformed strings.

Read the main() function carefully to understand how the functions will be used and what is expected from them.

Hints

<details> <summary>Click here to reveal hints</summary>

  • Use the filter method for filtering elements based on a condition.

  • Make sure you dereference the values when using them in the closure. For example:

    .filter(|&x| x % 2 != 0)

    Or

    .filter(|x| *x % 2 != 0)

  • Use the collect method to gather results from an iterator into a vector.

  • Use the map method for transforming elements in an iterator.

  • Use the to_uppercase method to convert a string to uppercase.

  • Define lifetimes for the input and output types in the function signature.

</details>
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pub fn filter_even_numbers(iter: impl Iterator<Item = i32>) -> Vec<i32> {
    // 1. Finish the function
}




// 2. Finish the function here
pub fn uppercase_strings


// Example usage
pub fn main() {
    // Filtering even numbers
    let numbers = vec![1, 2, 3, 4, 5];
    let odd_numbers = filter_even_numbers(numbers.into_iter());
    println!("{:?}", odd_numbers); // Should print: [1, 3, 5]


    // Converting strings to uppercase
    let words = vec!["hello", "world"];
    let uppercase_words = uppercase_strings(words.into_iter());
    println!("{:?}", uppercase_words); // Should print: ["HELLO", "WORLD"]
}