<p>Given an array of strings <code>words</code> representing an English Dictionary, return <em>the longest word in</em> <code>words</code> <em>that can be built one character at a time by other words in</em> <code>words</code>.</p>

<p>If there is more than one possible answer, return the longest word with the smallest lexicographical order. If there is no answer, return the empty string.</p>

<p>Note that the word should be built from left to right with each additional character being added to the end of a previous word.&nbsp;</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;w&quot;,&quot;wo&quot;,&quot;wor&quot;,&quot;worl&quot;,&quot;world&quot;]
<strong>Output:</strong> &quot;world&quot;
<strong>Explanation:</strong> The word &quot;world&quot; can be built one character at a time by &quot;w&quot;, &quot;wo&quot;, &quot;wor&quot;, and &quot;worl&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> words = [&quot;a&quot;,&quot;banana&quot;,&quot;app&quot;,&quot;appl&quot;,&quot;ap&quot;,&quot;apply&quot;,&quot;apple&quot;]
<strong>Output:</strong> &quot;apple&quot;
<strong>Explanation:</strong> Both &quot;apply&quot; and &quot;apple&quot; can be built from other words in the dictionary. However, &quot;apple&quot; is lexicographically smaller than &quot;apply&quot;.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= words.length &lt;= 1000</code></li>
	<li><code>1 &lt;= words[i].length &lt;= 30</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
</ul>

// #define ALPHABET_SIZE 26

// struct TrieNode {
//     vector<int> children(ALPHABET_SIZE);
//     bool isEndOfWord;
//     TrieNode() {
//         isEndOfWord = false;
//     }
// };

// class Trie {
// private:
//     TrieNode* root;
// public:
//     Trie() {
//         root = new TrieNode();
//     }
//     void insert(const string& word) {
//         TrieNode* currNode = root;
//         for (auto letter: word) {
//             if (currNode -> children[letter - 'a'] != NULL) {
//                 currNode = currNode -> children[letter - 'a'];
//             }
//             else {
//                 TrieNode* child = new TrieNode();
//                 currNode -> children[letter - 'a'] = child;
//                 currNode = child;
//             }
//         }
//     }
// }
class Solution {
public:
    string longestWord(vector<string>& words) {
       map<string, bool> isWordInDictionary;
       for (auto word : words) {
           isWordInDictionary[word] = true;
       }
       sort(words.begin(), words.end());
       int maxlen = 0;
       string answer = "";
       for(auto word : words) {
           string prefix = "";
           bool allPrefixesPresent = true;
           for (auto letter : word) {
               prefix += letter;
               if (!isWordInDictionary[prefix]) {
                   allPrefixesPresent = false;
                   break;
               }
           }
           if(allPrefixesPresent and word.length() > maxlen) {
               answer = word;
               maxlen = word.length();
           }
       }
        return answer;
    }
};
25003