Rewrite Heap.rs

[k12ish]

This trivial test fails:

#[test]
fn test_empty_heap() {
    let mut heap = MaxHeap::new::<i32>();
    assert_eq!(heap.next(), None)
}

---- data_structures::heap::tests::test_empty_heap stdout ----
thread 'data_structures::heap::tests::test_empty_heap' panicked at 'attempt to subtract with
overflow', src/data_structures/heap.rs:117:9

Other big issues:

• Vec contains a length meaning that count is unneeded
• The trait bound Default can be entirely removed with zero-based indexing, saving memory and making the implementation more flexible

I am more than happy to enact these changes, if that is acceptable to you.

[stale]

This issue has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[siriak]

Hi, you can make a PR to fix that and I'll get it reviewed and merged. Thanks for sharing!

[pdogr]

Hi I made a PR to fix this. Let me know if any other changes are required.
Thanks!

[siriak]

Cool, thanks! Feel free to make more PRs if you want to fix something else