Exercise - Implement an iterator

  • 4 minutes

In this exercise, you'll implement an iterator that returns equal items in a sequence grouped in vectors, such as:

  • Input: [ 1, 1, 2, 1, 3, 3 ]
  • Output: [ [1, 1], [2], [1], [3, 3] ]

Your goal is to finish writing the implementation of the Iterator trait for the Group struct, which will be responsible for keeping the data state in its inner field between iterations.

The generic type T will need to be an implementor of the trait PartialEq since you'll need to compare values to perform this assignment. But don't worry about that, because that part is already solved for you at the impl<T: PartialEq> segment.

struct Groups<T> {
    inner: Vec<T>,
}

impl<T> Groups<T> {
    fn new(inner: Vec<T>) -> Self {
	    Groups { inner }
    }
}

impl<T: PartialEq> Iterator for Groups<T> {
    type Item = Vec<T>;

    // TODO: Write the rest of this implementation.
}

fn main() {
    let data = vec![4, 1, 1, 2, 1, 3, 3, -2, -2, -2, 5, 5];
    // groups:     |->|---->|->|->|--->|----------->|--->|
    assert_eq!(
	    Groups::new(data).into_iter().collect::<Vec<Vec<_>>>(),
	    vec![
	        vec![4],
    	    vec![1, 1],
	        vec![2],
    	    vec![1],
	        vec![3, 3],
	        vec![-2, -2, -2],
    	    vec![5, 5],
	    ]
    );

    let data2 = vec![1, 2, 2, 1, 1, 2, 2, 3, 4, 4, 3];
    // groups:      |->|---->|---->|----|->|----->|->|
    assert_eq!(
	    Groups::new(data2).into_iter().collect::<Vec<Vec<_>>>(),
	    vec![
	        vec![1],
    	    vec![2, 2],
	        vec![1, 1],
	        vec![2, 2],
    	    vec![3],
	        vec![4, 4],
	        vec![3],
	    ]
    )
}

You can also view this exercise at this Rust Playground link.

To find a solution for this exercise, check out this Rust Playground link.