20240630 Finished

src/problem/mod.rs

@@ -161,4 +161,5 @@ mod p207_course_schedule;
 mod p210_course_schedule_ii;
 mod p909_snakes_and_ladders;
 mod p433_minimum_genetic_mutation;
-mod p127_word_ladder;
+mod p127_word_ladder;
+mod p208_implement_trie_prefix_tree;

src/problem/p208_implement_trie_prefix_tree.rs

@@ -0,0 +1,126 @@
+/**
+ * [208] Implement Trie (Prefix Tree)
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::{cell::RefCell, collections::HashMap, rc::Rc};
+
+#[derive(Debug)]
+struct TrieNode {
+    is_ended: bool,
+    next: HashMap<char, Rc<RefCell<TrieNode>>>,
+}
+
+impl TrieNode {
+    fn new(is_ended: bool) -> Self {
+        TrieNode {
+            is_ended,
+            next: HashMap::new(),
+        }
+    }
+}
+
+struct Trie {
+    head: Rc<RefCell<TrieNode>>,
+}
+
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl Trie {
+    fn new() -> Self {
+        Trie {
+            head: Rc::new(RefCell::new(TrieNode::new(false))),
+        }
+    }
+
+    fn insert(&mut self, word: String) {
+        let mut node = Rc::clone(&self.head);
+
+        for (i, c) in word.chars().enumerate() {
+            if node.borrow().next.contains_key(&c) {
+                if i == word.len() - 1 {
+                    node.borrow().next.get(&c).unwrap().borrow_mut().is_ended = true;
+                }
+            } else {
+                if i == word.len() - 1 {
+                    node.borrow_mut()
+                        .next
+                        .insert(c, Rc::new(RefCell::new(TrieNode::new(true))));
+                } else {
+                    node.borrow_mut()
+                        .next
+                        .insert(c, Rc::new(RefCell::new(TrieNode::new(false))));
+                }
+            }
+
+            let tmp_node = Rc::clone(node.borrow().next.get(&c).unwrap());
+            node = tmp_node;
+        }
+    }
+
+    fn search(&self, word: String) -> bool {
+        let mut node = Rc::clone(&self.head);
+
+        for (i, c) in word.chars().enumerate() {
+            if !node.borrow().next.contains_key(&c) {
+                return false;
+            }
+
+            if i == word.len() - 1 {
+                if !node.borrow().next.get(&c).unwrap().borrow().is_ended {
+                    return false;
+                }
+            }
+
+            let tmp_node = Rc::clone(node.borrow().next.get(&c).unwrap());
+            node = tmp_node;
+        }
+
+        true
+    }
+
+    fn starts_with(&self, prefix: String) -> bool {
+        let mut node = Rc::clone(&self.head);
+
+        for c in prefix.chars() {
+            if !node.borrow().next.contains_key(&c) {
+                return false;
+            }
+
+            let tmp_node = Rc::clone(node.borrow().next.get(&c).unwrap());
+            node = tmp_node;
+        }
+
+        true
+    }
+}
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * let obj = Trie::new();
+ * obj.insert(word);
+ * let ret_2: bool = obj.search(word);
+ * let ret_3: bool = obj.starts_with(prefix);
+ */
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_208() {
+        let mut trie = Trie::new();
+
+        trie.insert("app".to_owned());
+
+        assert!(!trie.search("ap".to_owned()));
+
+        trie.insert("ap".to_owned());
+        assert!(trie.search("ap".to_owned()));
+    }
+}