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use std::collections::HashMap;
use std::hash::Hash;
use std::slice;
pub(crate) struct UniqueTable<'entries, T: Eq + Hash> {
table: Vec<&'entries T>,
map: HashMap<&'entries T, usize>,
}
impl<'entries, T: Eq + Hash> UniqueTable<'entries, T> {
pub fn new() -> Self {
Self {
table: Vec::new(),
map: HashMap::new(),
}
}
pub fn add(&mut self, entry: &'entries T) -> usize {
match self.map.get(&entry) {
None => {
let i = self.table.len();
self.table.push(entry);
self.map.insert(entry, i);
i
}
Some(&i) => i,
}
}
pub fn len(&self) -> usize {
self.table.len()
}
pub fn iter(&self) -> slice::Iter<&'entries T> {
self.table.iter()
}
}
pub(crate) struct UniqueSeqTable<T: PartialEq + Clone> {
table: Vec<T>,
}
impl<T: PartialEq + Clone> UniqueSeqTable<T> {
pub fn new() -> Self {
Self { table: Vec::new() }
}
pub fn add(&mut self, values: &[T]) -> usize {
if values.is_empty() {
return 0;
}
if let Some(offset) = find_subsequence(values, &self.table) {
offset
} else {
let table_len = self.table.len();
let mut start_from = usize::min(table_len, values.len() - 1);
while start_from != 0 {
if values[0..start_from] == self.table[table_len - start_from..table_len] {
break;
}
start_from -= 1;
}
self.table
.extend(values[start_from..values.len()].iter().cloned());
table_len - start_from
}
}
pub fn len(&self) -> usize {
self.table.len()
}
pub fn iter(&self) -> slice::Iter<T> {
self.table.iter()
}
}
fn find_subsequence<T: PartialEq>(sub: &[T], whole: &[T]) -> Option<usize> {
assert!(!sub.is_empty());
if whole.len() < sub.len() {
return None;
}
let max = whole.len() - sub.len();
for i in 0..=max {
if whole[i..i + sub.len()] == sub[..] {
return Some(i);
}
}
None
}
#[test]
fn test_find_subsequence() {
assert_eq!(find_subsequence(&vec![1], &vec![4]), None);
assert_eq!(find_subsequence(&vec![1], &vec![1]), Some(0));
assert_eq!(find_subsequence(&vec![1, 2], &vec![1]), None);
assert_eq!(find_subsequence(&vec![1, 2], &vec![1, 2]), Some(0));
assert_eq!(find_subsequence(&vec![1, 2], &vec![1, 3]), None);
assert_eq!(find_subsequence(&vec![1, 2], &vec![0, 1, 2]), Some(1));
assert_eq!(find_subsequence(&vec![1, 2], &vec![0, 1, 3, 1]), None);
assert_eq!(find_subsequence(&vec![1, 2], &vec![0, 1, 3, 1, 2]), Some(3));
assert_eq!(
find_subsequence(&vec![1, 1, 3], &vec![1, 1, 1, 3, 3]),
Some(1)
);
}
#[test]
fn test_optimal_add() {
let mut seq_table = UniqueSeqTable::new();
assert_eq!(seq_table.add(&vec![0, 1, 2, 3]), 0);
assert_eq!(seq_table.add(&vec![0, 1, 2, 3]), 0);
assert_eq!(seq_table.add(&vec![1, 2, 3]), 1);
assert_eq!(seq_table.add(&vec![2, 3]), 2);
assert_eq!(seq_table.len(), 4);
assert_eq!(seq_table.add(&vec![2, 3, 4]), 2);
assert_eq!(seq_table.len(), 5);
assert_eq!(seq_table.add(&vec![4, 6, 5, 7]), 4);
assert_eq!(seq_table.len(), 8);
assert_eq!(seq_table.add(&vec![8, 2, 3, 4]), 8);
assert_eq!(seq_table.add(&vec![8]), 8);
assert_eq!(seq_table.len(), 12);
}