When we iterate over HashMap<usize, T> it's not always ordered. Same for BTreeMap. Are there ways for doing the iteration in order like 0,1,2,3, etc for the keys?
Found a good answer on SO:
A BTreeMap is always ordered by keys. There is no ordering for a HashMap.
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You could use IndexMap: it's a HashMap that maintains insertion order, but you can also call sort_keys as needed. I would try to batch that though, as it's a fairly heavy operation.
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