235th Commit

README.md

@@ -40,13 +40,13 @@ $ pnpm test twoSum.test.ts
 - [樹 (Tree)](./algorithms/tree/README.md)
 - [堆積 (Heap)](./algorithms/heap/README.md)
 - [圖 (Graph)](./algorithms/graph/README.md)
-- 字典樹 (Trie)
+- [字典樹 (Trie)](./algorithms/trie/README.md)
 - 排序 (Sorting)
 - [搜尋 (Searching)](./algorithms/searching/README.md)
+- 分治 (Divide and Conquer)
+- 回溯 (Backtracking)
 - [動態規劃 (Dynamic Programming)](./algorithms/dynamic-programming/README.md)
 - 貪婪 (Greedy)
-- 回溯 (Backtracking)
-- 分治 (Divide and Conquer)
 - 位元操作 (Bit Manipulation)
 
 ## Basic - LeetCode 75

algorithms/trie/README.md

@@ -0,0 +1,78 @@
+# 字典樹 (Trie)
+
+```ts
+class TrieNode {
+  children: Map<string, TrieNode>;
+  isEndOfWord: boolean;
+
+  constructor() {
+    this.children = new Map();
+    this.isEndOfWord = false;
+  }
+}
+```
+
+```ts
+class Trie {
+  root: TrieNode;
+
+  constructor() {
+    this.root = new TrieNode();
+  }
+
+  // 插入字詞
+  insert(word: string): void {
+    let current = this.root;
+
+    for (const char of word) {
+      if (!current.children.has(char)) {
+        current.children.set(char, new TrieNode());
+      }
+
+      current = current.children.get(char) as TrieNode;
+    }
+
+    current.isEndOfWord = true;
+  }
+
+  // 查找字
+  search(word: string): boolean {
+    let current = this.root;
+
+    for (const char of word) {
+      if (!current.children.has(char)) return false;
+      current = current.children.get(char) as TrieNode;
+    }
+
+    return current.isEndOfWord;
+  }
+
+  // 查找是否存在某個前綴
+  startsWith(prefix: string): boolean {
+    let current = this.root;
+
+    for (const char of prefix) {
+      if (!current.children.has(char)) return false;
+      current = current.children.get(char) as TrieNode;
+    }
+
+    return true;
+  }
+}
+```
+
+```ts
+const trie = new Trie();
+
+trie.insert('apple');
+trie.insert('banana');
+
+console.log(trie.search('apple')); // true
+console.log(trie.search('app')); // false
+console.log(trie.search('banana')); // true
+
+console.log(trie.startsWith('app')); // true
+
+trie.insert('app');
+console.log(trie.search('app')); // true
+```

algorithms/trie/Trie.ts

@@ -0,0 +1,48 @@
+import { TrieNode } from './TrieNode';
+
+export class Trie {
+  root: TrieNode;
+
+  constructor() {
+    this.root = new TrieNode();
+  }
+
+  // 插入字詞
+  insert(word: string): void {
+    let current = this.root;
+
+    for (const char of word) {
+      if (!current.children.has(char)) {
+        current.children.set(char, new TrieNode());
+      }
+
+      current = current.children.get(char) as TrieNode;
+    }
+
+    current.isEndOfWord = true;
+  }
+
+  // 查找字
+  search(word: string): boolean {
+    let current = this.root;
+
+    for (const char of word) {
+      if (!current.children.has(char)) return false;
+      current = current.children.get(char) as TrieNode;
+    }
+
+    return current.isEndOfWord;
+  }
+
+  // 查找是否存在某個前綴
+  startsWith(prefix: string): boolean {
+    let current = this.root;
+
+    for (const char of prefix) {
+      if (!current.children.has(char)) return false;
+      current = current.children.get(char) as TrieNode;
+    }
+
+    return true;
+  }
+}

algorithms/trie/TrieNode.ts

@@ -0,0 +1,9 @@
+export class TrieNode {
+  children: Map<string, TrieNode>;
+  isEndOfWord: boolean;
+
+  constructor() {
+    this.children = new Map();
+    this.isEndOfWord = false;
+  }
+}