TODO optimize the performance for very large item lists #1
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alexandruradovici
requested changes
Jan 7, 2024
| /// | ||
| /// ```ignore | ||
| /// table.set_on_sort(|siv: &mut Cursive, column: BasicColumn, order: Ordering| { | ||
| /// ```rust |
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Any reason why these are modified?
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I saw that one of the tests ignored from the beginning was solved and I modified it to solve this one as well
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| let reverse_mapping: HashMap<usize, usize> = self.rows_to_items.iter().enumerate().map(|(row, &item)| (item, row)).collect(); | ||
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| // Use the reverse mapping to find the row corresponding to the item_index | ||
| if let Some(&row) = reverse_mapping.get(&item_index) { | ||
| self.focus = row; | ||
| self.scroll_core.scroll_to_y(row); |
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Unless you always keep the hasmap up to date when adding and deleting items, this is slower than the original code. It does one O(n) traversal to build the hashmap, and for each item an O(log n) to insert into the hasmap. It does another O(log n) to retrieve the item.
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This approach uses a HashMap to create an inverse mapping between the index of an element and the corresponding row in a list. When you want to set a selected element by index, you can directly use the reverse map to find the corresponding row without traversing the entire list.