add 208 js, go and some explain for cpp

Author: luliyucoordinate

README.md

@@ -186,10 +186,11 @@ LeetCode
 |0205|[Isomorphic Strings](https://leetcode.com/problems/isomorphic-strings/) | c | [c++](./src/0205-Isomorphic-Strings/0205.cpp) |[python](./src/0205-Isomorphic-Strings/0205.py)|||Easy|
 |0206|[Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/) | c | [c++](./src/0206-Reverse-Linked-List/0206.cpp) |[python](./src/0206-Reverse-Linked-List/0206.py)|||Easy|
 |0207|[Course Schedule](https://leetcode.com/problems/course-schedule/) | c | [c++](./src/0207-Course-Schedule/0207.cpp) |[python](./src/0207-Course-Schedule/0207.py)|[go](./src/0207-Course-Schedule/0207.go)|[js](./src/0207-Course-Schedule/0207.js)|Medium|
-|0208|[Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) | c | [c++](./src/0208-Implement-Trie-(Prefix-Tree)/0208.cpp) |[python](./src/0208-Implement-Trie-(Prefix-Tree)/0208.py)|||Easy|
+|0208|[Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/) | c | [c++](./src/0208-Implement-Trie-(Prefix-Tree)/0208.cpp) |[python](./src/0208-Implement-Trie-(Prefix-Tree)/0208.py)|||Medium|
 |0209|[Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/) | c | [c++](./src/0209-Minimum-Size-Subarray-Sum/0209.cpp) |[python](./src/0209-Minimum-Size-Subarray-Sum/0209.py)|||Medium|
 |0210|[Course Schedule II](https://leetcode.com/problems/course-schedule-ii/) | c | [c++](./src/0210-Course-Schedule-II/0210.cpp) |[python](./src/0210-Course-Schedule-II/0210.py)|[go](./src/0210-Course-Schedule-II/0210.go)|[js](./src/0210-Course-Schedule-II/0210.js)|Medium|
 |0211|[Add and Search Word - Data structure design](https://leetcode.com/problems/add-and-search-word-data-structure-design/) | c | [c++](./src/0211-Add-and-Search-Word-Data-structure-design/0211.cpp) |[python](./src/0211-Add-and-Search-Word-Data-structure-design/0211.py)|||Medium|
+|0212|[Word Search II](https://leetcode.com/problems/word-search-ii/) | c | [c++](./src/0212-Word-Search-II/0212.cpp) |[python](./src/0212-Word-Search-II/0212.py)|[go](./src/0212-Word-Search-II/0212.go)|[js](./src/0212-Word-Search-II/0212.js)|Medium|
 |0213|[House Robber II](https://leetcode.com/problems/house-robber-ii/) | c | [c++](./src/0213-House-Robber-II/0213.cpp) |[python](./src/0213-House-Robber-II/0213.py)|||Medium|
 |0215|[Kth Largest Element in an Array](https://leetcode.com/problems/kth-largest-element-in-an-array/) | c | [c++](./src/0215-Kth-Largest-Element-in-an-Array/0215.cpp) |[python](./src/0215-Kth-Largest-Element-in-an-Array/0215.py)|||Medium|
 |0216|[Combination Sum III](https://leetcode.com/problems/combination-sum-iii/) | c | [c++](./src/0216-Combination-Sum-III/0216.cpp) |[python](./src/0216-Combination-Sum-III/0216.py)|||Medium|

src/0208-Implement-Trie-(Prefix-Tree)/0208.cpp

@@ -26,7 +26,8 @@ class Trie
         auto cur = _root;
         for (auto c : word)
         {
-            if (!(cur->next).count(c)) cur->next[c] = new Node();
+            if (!(cur->next).count(c)) // or if (cur->next[c] == nullptr)
+                cur->next[c] = new Node();   
             cur = cur->next[c];
         }
         if (!cur->isWord) cur->isWord = true;

src/0208-Implement-Trie-(Prefix-Tree)/0208.go

@@ -0,0 +1,55 @@
+type Trie struct {
+    next map[rune]*Trie
+    isWord bool
+}
+
+
+/** Initialize your data structure here. */
+func Constructor() Trie {
+    return Trie{next: make(map[rune]*Trie)}
+}
+
+
+/** Inserts a word into the trie. */
+func (this *Trie) Insert(word string)  {
+    cur := this
+    for _, c := range word {
+        if cur.next[c] == nil {
+            cur.next[c] = &Trie{next: make(map[rune]*Trie)}
+        }
+        cur = cur.next[c]
+    }
+    if !cur.isWord {
+        cur.isWord = true
+    }
+}
+
+
+func (this *Trie) search(word string) *Trie {
+    cur := this
+    for _, c := range word {
+        if cur.next[c] == nil {
+            return nil
+        }
+        cur = cur.next[c]
+    }
+    return cur
+}
+
+/** Returns if the word is in the trie. */
+func (this *Trie) Search(word string) bool {
+    cur := this.search(word)
+    if cur != nil && cur.isWord {
+        return true
+    }
+    return false
+}
+
+
+/** Returns if there is any word in the trie that starts with the given prefix. */
+func (this *Trie) StartsWith(prefix string) bool {
+    if this.search(prefix) != nil {
+        return true
+    }
+    return false
+}

src/0208-Implement-Trie-(Prefix-Tree)/0208.js

@@ -0,0 +1,54 @@
+/**
+ * Initialize your data structure here.
+ */
+var Trie = function() {
+    this.next = {};
+    this.isWord = false;
+};
+
+/**
+ * Inserts a word into the trie. 
+ * @param {string} word
+ * @return {void}
+ */
+Trie.prototype.insert = function(word) {
+    let cur = this;
+    for (let c of word) {
+        if (!cur.next[c]) {
+            cur.next[c] = new Trie();
+        }
+        cur = cur.next[c];
+    }
+    if (!cur.isWord) cur.isWord = true;
+};
+
+
+Trie.prototype.find = function(word) {
+    let cur = this;
+    for (let c of word) {
+        if (!cur.next[c]) return null;
+        cur = cur.next[c];
+    }
+    return cur;
+};
+
+/**
+ * Returns if the word is in the trie. 
+ * @param {string} word
+ * @return {boolean}
+ */
+Trie.prototype.search = function(word) {
+    let cur = this.find(word);
+    if (cur != null && cur.isWord) return true;
+    return false;
+};
+
+/**
+ * Returns if there is any word in the trie that starts with the given prefix. 
+ * @param {string} prefix
+ * @return {boolean}
+ */
+Trie.prototype.startsWith = function(prefix) {
+    if (this.find(prefix) != null) return true;
+    return false;
+};