add leetcode implement trie solution

Author: arka-bhat

Trie/(Leetcode) 208_Implement_Trie_(Prefix_Tree).cpp

@@ -0,0 +1,67 @@
+/**
+ * A trie (pronounced as "try") or prefix tree is a tree data structure used to efficiently store and retrieve keys in a dataset of strings. 
+ * There are various applications of this data structure, such as autocomplete and spellchecker
+ *
+ * Your Trie object will be instantiated and called as such:
+ * Trie* obj = new Trie();
+ * obj->insert(word);
+ * bool param_2 = obj->search(word);
+ * bool param_3 = obj->startsWith(prefix);
+ */
+
+class Trie {
+public:
+    struct TrieNode
+    {
+        TrieNode* child[26];
+        bool isEnd;
+        TrieNode()
+        {
+            isEnd = false;
+            for(int i = 0; i < 26; i++)
+                child[i] = NULL;
+        }
+    };
+    
+    TrieNode* root;
+    
+    Trie() {
+        root = new TrieNode();
+    }
+    
+    void insert(string word) {
+        TrieNode* curr = root;
+        for(int i = 0; i < word.length(); i++)
+        {
+            int index = word[i] - 'a';
+            if(curr->child[index] == NULL)
+                curr->child[index] = new TrieNode();
+            curr = curr->child[index];
+        }
+        curr->isEnd = true;
+    }
+    
+    bool search(string word) {
+        TrieNode* curr = root;
+        for(int i = 0; i < word.length(); i++)
+        {
+            int index = word[i] - 'a';
+            if(curr->child[index] == NULL)
+                return false;
+            curr = curr->child[index];
+        }
+        return curr->isEnd;
+    }
+    
+    bool startsWith(string prefix) {
+        TrieNode* curr = root;
+        for(int i = 0; i < prefix.length(); i++)
+        {
+            int index = prefix[i] - 'a';
+            if(curr->child[index] == NULL)
+                return false;
+            curr = curr->child[index];
+        }
+        return true;
+    }
+};