✨ [209] PREFIX TREE BY MYSELF!

Author: enkr1

209/my_solution.js

@@ -0,0 +1,106 @@
+class Trie {
+  constructor() {
+    const LENGTH = 26;
+    this.isEndOfWord = false;
+    this.children = new Array(LENGTH).fill(null);
+  }
+
+  getIdx(char) {
+    return char.charCodeAt() - "a".charCodeAt();
+  }
+
+  /**
+   * @param {string} word
+   * @return {void}
+   */
+  insert(word) {
+    let root = this;
+    for (let i = 0; i < word.length; i++) {
+      let idx = this.getIdx(word[i]);
+      console.log(`word:${word[i]}, idx:${idx}`)
+      if (root.children[idx] === null) root.children[idx] = new Trie();
+      root = root.children[idx];
+    }
+    root.isEndOfWord = true;
+    // console.log(this)
+  }
+
+  /**
+   * @param {string} word
+   * @return {boolean}
+   */
+  search(word) {
+    console.log(`Searching "${word}" ...`)
+    const dfs = (i, node) => {
+      // if (i === word.length) return false;
+      console.log(`i:${i}, word:${word[i]}`)
+      console.log(node)
+      if (word[i] === undefined) return node.isEndOfWord;
+
+      let child = node.children[this.getIdx(word[i])];
+      if (node.isEndOfWord && i === word.length) return true;
+      if (null === child) return false;
+      // console.log(child)
+
+      return dfs(i + 1, child);
+    }
+
+    return dfs(0, this);
+  }
+
+  /**
+   * @param {string} prefix
+   * @return {boolean}
+   */
+  startsWith(prefix) {
+    const dfs = (i, node) => {
+      console.log(`i:${i}, prefix:${prefix[i]}`)
+      if (prefix[i] === undefined) return !(null === node);
+
+      let child = node.children[this.getIdx(prefix[i])];
+      if (node.isEndOfWord && i === prefix.length) return true;
+      if (null === child) return false;
+
+      return dfs(i + 1, child);
+    }
+
+    return dfs(0, this);
+  }
+}
+
+
+
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * var obj = new Trie()
+ * obj.insert(word)
+ * var param_2 = obj.search(word)
+ * var param_3 = obj.startsWith(prefix)
+ */
+
+var obj = new Trie()
+obj.insert("hello")
+// obj.insert("a")
+console.log(obj.search("helloa"))
+// obj.insert("wor")
+// // console.log(obj.children[22].children[14].children[17]) // 17,3
+// console.log(obj.search("wor"))
+// console.log(obj.search("wo"))
+// console.log(obj.startsWith("z"))
+
+// [
+//   "Trie",
+//   "insert",
+//   "search", "search", "search",
+//   "startsWith", "startsWith", "startsWith"]
+// [
+//   [],
+//   ["hello"],
+//   ["hell"], ["helloa"], ["hello"],
+//   ["hell"], ["helloa"], ["hello"]]
+// [
+//   null,
+//   null,
+//   false, false, true,
+//   true, false, true]

209/solution.js

@@ -0,0 +1,61 @@
+class Trie {
+  constructor() {
+    const LENGTH = 26;
+    this.isEndOfWord = false;
+    this.children = new Array(LENGTH).fill(null);
+  }
+
+  getIdx(char) {
+    return char.charCodeAt() - "a".charCodeAt();
+  }
+
+  /**
+   * @param {string} word
+   * @return {void}
+   */
+  insert(word) {
+    let root = this;
+    for (let i = 0; i < word.length; i++) {
+      let idx = this.getIdx(word[i]);
+      if (root.children[idx] === null) root.children[idx] = new Trie();
+      root = root.children[idx];
+    }
+    root.isEndOfWord = true;
+  }
+
+  /**
+   * @param {string} word
+   * @return {boolean}
+   */
+  search(word) {
+    const dfs = (i, node) => {
+      if (word[i] === undefined) return node.isEndOfWord;
+
+      let child = node.children[this.getIdx(word[i])];
+      if (node.isEndOfWord && i === word.length) return true;
+      if (null === child) return false;
+
+      return dfs(i + 1, child);
+    }
+
+    return dfs(0, this);
+  }
+
+  /**
+   * @param {string} prefix
+   * @return {boolean}
+   */
+  startsWith(prefix) {
+    const dfs = (i, node) => {
+      if (prefix[i] === undefined) return !(null === node);
+
+      let child = node.children[this.getIdx(prefix[i])];
+      if (node.isEndOfWord && i === prefix.length) return true;
+      if (null === child) return false;
+
+      return dfs(i + 1, child);
+    }
+
+    return dfs(0, this);
+  }
+}

README.md

@@ -56,6 +56,7 @@
 - [200. Number of Islands](./200/)
 - [206. Reverse Linked List](./206/)
 - [207. Course Schedule](./207/)
+- [208. Implement Trie (Prefix Tree)](./209/)
 - [211. Design Add and Search Words Data Structure](./211/)
 - [213. House Robber II](./213/)
 - [217. Contains Duplicate](./217/)
@@ -147,7 +148,7 @@ Batch create:
 NOTE: JS IS HERE
 -->
 ```ssh
-chapter=211 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
+chapter=209 && mkdir ./$chapter && touch ./$chapter/my_solution.js && touch ./$chapter/solution.js && alias x="node ./$chapter/my_solution.js"
 ```
 > then you can use `x` for quick debug.
 

test.js

@@ -54,13 +54,19 @@
 // o[2] = [1, 3, 4]
 // console.log(o)
 //
-let x = Array(3).fill([]);
-x[1].push(2)
-// x[1] = 2
-console.log(x)
+// let x = Array(3).fill([]);
+// x[1].push(2)
+// // x[1] = 2
+// console.log(x)
 //
-// const g = Array(3).fill().map(() => []);
-// console.log(g)
+n = 5;
+const g =
+  // Array(n).fill([]);
+// Array(n).fill().map(() => []);
+Array.from({ length: n }, () => []);
+g[1].push(2)
+
+console.log(g)
 
 
 // Set
@@ -75,8 +81,13 @@ console.log(x)
 // console.log(set.has([1, 2]))
 // console.log(set.has(x))
 
-// Map
-// console.log(new Map([["key", "value"], ["rrsrsr", true]]))
+// // Map
+// let map = new Map([["key", "value"], ["rrsrsr", true]])
+// console.log(map)
+// console.log(map.values()) // "value", true
+// for (let value of map.values()) {
+//   console.log(`in loop:${value}`)
+// }
 
 // Array
 // let l = [];