You need to understand what a Trie is before writing the code :-) has a nice solution, whose code is rewritten below.

1 class TrieNode { 2 public: 3     bool isWord; 4     TrieNode* children[26]; 5     // Initialize your data structure here. 6     TrieNode() : isWord(false) { 7         memset(children, NULL, sizeof(TrieNode*) * 26); 8     } 9 };10 11 class Trie {12 public:13     Trie() {14         root = new TrieNode();15     }16 17     // Inserts a word into the trie.18     void insert(string word) {19         TrieNode* run = root;20         for (char c : word) {21             if (!(run -> children[c - 'a']))22                 run -> children[c - 'a'] = new TrieNode();23             run = run -> children[c - 'a'];24         }25         run -> isWord = true;26     }27 28     // Returns if the word is in the trie.29     bool search(string word) {30         TrieNode* p = query(word);31         return p && p -> isWord;32     }33 34     // Returns if there is any word in the trie35     // that starts with the given prefix.36     bool startsWith(string prefix) {37         return query(prefix);38     }39 40 private:41     TrieNode* root;42     TrieNode* query(string& s) {43         TrieNode* run = root;44         for (char c : s) {45             if (!(run -> children[c - 'a'])) return NULL;46             run = run -> children[c - 'a'];47         }48         return run;49     }50 };51 52 // Your Trie object will be instantiated and called as such:53 // Trie trie;54 // trie.insert("somestring");55 // trie.search("key");