45 lines
1.2 KiB
Rust
45 lines
1.2 KiB
Rust
pub trait InsertMany {
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type Element;
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fn insert_many(&mut self, elem_to_insert: Vec<(usize, Self::Element)>);
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}
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impl<T> InsertMany for Vec<T> {
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type Element = T;
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/// Efficiently insert multiple element in their specified index.
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/// The elements should sorted in ascending order by their index.
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///
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/// This is done in O(n) time.
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fn insert_many(&mut self, elem_to_insert: Vec<(usize, T)>) {
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let mut inserted = vec![];
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let mut last_idx = 0;
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for (idx, elem) in elem_to_insert.into_iter() {
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let head_len = idx - last_idx;
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inserted.extend(self.splice(0..head_len, std::iter::empty()));
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inserted.push(elem);
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last_idx = idx;
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}
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let len = self.len();
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inserted.extend(self.drain(0..len));
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*self = inserted;
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}
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}
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#[cfg(test)]
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mod test {
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use super::InsertMany;
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#[test]
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fn insert_many_works() {
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let mut v = vec![1, 2, 3, 4, 5];
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v.insert_many(vec![(0, 0), (2, -1), (5, 6)]);
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assert_eq!(v, &[0, 1, 2, -1, 3, 4, 5, 6]);
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let mut v2 = vec![1, 2, 3, 4, 5];
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v2.insert_many(vec![(0, 0), (2, -1)]);
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assert_eq!(v2, &[0, 1, 2, -1, 3, 4, 5]);
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}
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}
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