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trie.rs
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trie.rs
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use crate::core::St;
use std::collections::HashMap;
#[derive(Debug, PartialEq)]
pub enum NodeKind {
None,
Prefix,
Terminal,
}
pub struct StTrie {
nodes: HashMap<St, bool>,
count: usize,
}
impl StTrie {
fn new() -> StTrie {
let nodes = HashMap::new();
let count = 0;
StTrie { nodes, count }
}
fn len(&self) -> usize {
self.count
}
fn insert(&mut self, value: St) {
if value.len() == 0 {
return;
}
if let Some(&true) = self.nodes.get(&value) {
return;
}
self.count += 1;
self.nodes.insert(value, true);
let mut value = value;
for _ in 1..value.len() {
value = value.chop();
if let Some(_) = self.nodes.get(&value) {
return;
}
self.nodes.insert(value, false);
}
}
fn find(&self, value: St) -> NodeKind {
match self.nodes.get(&value) {
None => NodeKind::None,
Some(&true) => NodeKind::Terminal,
Some(&false) => NodeKind::Prefix,
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn empty() {
let trie = init_trie(vec![]);
assert_eq!(0, trie.len());
}
#[test]
fn one_item_len_1() {
let trie = init_trie(vec!["X"]);
assert_eq!(1, trie.len());
}
#[test]
fn two_items_len_2_shared_prefix() {
let trie = init_trie(vec!["HI", "HA"]);
assert_eq!(2, trie.len());
assert_eq!(NodeKind::Prefix, find_trie(&trie, "H"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "HA"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "HI"));
}
#[test]
fn two_items_len_3_no_shared_prefix() {
let trie = init_trie(vec!["ABC", "DEF", "GHI"]);
assert_eq!(3, trie.len());
assert_eq!(NodeKind::Prefix, find_trie(&trie, "A"));
assert_eq!(NodeKind::Prefix, find_trie(&trie, "AB"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "ABC"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "DEF"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "GHI"));
}
#[test]
fn get_nonexistent_node() {
let trie = init_trie(vec!["ABC"]);
assert_eq!(NodeKind::None, find_trie(&trie, "X"));
}
#[test]
fn add_nodes_multiple_times() {
let trie = init_trie(vec!["AB", "AB", "ABC", "ABC"]);
assert_eq!(2, trie.len());
assert_eq!(NodeKind::Prefix, find_trie(&trie, "A"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "AB"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "ABC"));
}
#[test]
fn add_nodes_multiple_times_longer_first() {
let trie = init_trie(vec!["ABC", "ABC", "AB", "AB"]);
assert_eq!(2, trie.len());
assert_eq!(NodeKind::Prefix, find_trie(&trie, "A"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "AB"));
assert_eq!(NodeKind::Terminal, find_trie(&trie, "ABC"));
}
#[test]
fn add_empty_node() {
let trie = init_trie(vec![""]);
assert_eq!(0, trie.len());
}
fn init_trie(items: Vec<&str>) -> StTrie {
let mut trie = StTrie::new();
for item in items {
trie.insert(item.parse::<St>().unwrap());
}
trie
}
fn find_trie(trie: &StTrie, item: &str) -> NodeKind {
trie.find(item.parse::<St>().unwrap())
}
}