design add and search words data structure solution

Author: yhkee0404

design-add-and-search-words-data-structure/yhkee0404.rs

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+use std::collections::HashMap;
+
+struct WordDictionary {
+    trie: Box<Trie>,
+}
+
+struct Trie {
+    ended: bool,
+    children: HashMap<char, Box<Trie>>,
+}
+
+
+/** 
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl WordDictionary {
+
+    fn new() -> Self {
+        WordDictionary {
+            trie: Box::new(Trie::new()),
+        }
+    }
+    
+    // T(n) = S(n) = O(26n) = O(n)
+    fn add_word(&mut self, word: String) {
+        let mut t = &mut self.trie;
+        for c in word.chars() {
+            t = t.children
+                    .entry(c)
+                    .or_insert(Box::new(Trie::new()))
+        }
+        t.ended = true
+    }
+    
+    fn search(&self, word: String) -> bool {
+        return Self::search_from_index(&self.trie, &word)
+    }
+
+    // T(n) = S(n) = ((2^2)n) = O(n)
+    fn search_from_index(trie: &Trie, word: &str) -> bool {
+        return match word.chars()
+                .next() {
+                    None => trie.ended,
+                    Some(c) => if c == '.' {
+                                trie.children
+                                .values()
+                                .any(|x| Self::search_from_index(&x, &word[1..])) // Slice O(1)
+                            } else {
+                                match trie.children
+                                        .get(&c) {
+                                            None => false,
+                                            Some(x) => Self::search_from_index(&x, &word[1..]), // Slice O(1)
+                                        }
+                            },
+                }
+    }
+}
+
+/**
+ * Your WordDictionary object will be instantiated and called as such:
+ * let obj = WordDictionary::new();
+ * obj.add_word(word);
+ * let ret_2: bool = obj.search(word);
+ */
+
+impl Trie {
+    fn new() -> Self {
+        Trie {
+            ended: false,
+            children: HashMap::new(),
+        }
+    }
+}