<p>You are given an array of strings <code>products</code> and a string <code>searchWord</code>.</p>

<p>Design a system that suggests at most three product names from <code>products</code> after each character of <code>searchWord</code> is typed. Suggested products should have common prefix with <code>searchWord</code>. If there are more than three products with a common prefix return the three lexicographically minimums products.</p>

<p>Return <em>a list of lists of the suggested products after each character of </em><code>searchWord</code><em> is typed</em>.</p>

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

<pre>
<strong>Input:</strong> products = [&quot;mobile&quot;,&quot;mouse&quot;,&quot;moneypot&quot;,&quot;monitor&quot;,&quot;mousepad&quot;], searchWord = &quot;mouse&quot;
<strong>Output:</strong> [[&quot;mobile&quot;,&quot;moneypot&quot;,&quot;monitor&quot;],[&quot;mobile&quot;,&quot;moneypot&quot;,&quot;monitor&quot;],[&quot;mouse&quot;,&quot;mousepad&quot;],[&quot;mouse&quot;,&quot;mousepad&quot;],[&quot;mouse&quot;,&quot;mousepad&quot;]]
<strong>Explanation:</strong> products sorted lexicographically = [&quot;mobile&quot;,&quot;moneypot&quot;,&quot;monitor&quot;,&quot;mouse&quot;,&quot;mousepad&quot;].
After typing m and mo all products match and we show user [&quot;mobile&quot;,&quot;moneypot&quot;,&quot;monitor&quot;].
After typing mou, mous and mouse the system suggests [&quot;mouse&quot;,&quot;mousepad&quot;].
</pre>

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

<pre>
<strong>Input:</strong> products = [&quot;havana&quot;], searchWord = &quot;havana&quot;
<strong>Output:</strong> [[&quot;havana&quot;],[&quot;havana&quot;],[&quot;havana&quot;],[&quot;havana&quot;],[&quot;havana&quot;],[&quot;havana&quot;]]
<strong>Explanation:</strong> The only word &quot;havana&quot; will be always suggested while typing the search word.
</pre>

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

<ul>
	<li><code>1 &lt;= products.length &lt;= 1000</code></li>
	<li><code>1 &lt;= products[i].length &lt;= 3000</code></li>
	<li><code>1 &lt;= sum(products[i].length) &lt;= 2 * 10<sup>4</sup></code></li>
	<li>All the strings of <code>products</code> are <strong>unique</strong>.</li>
	<li><code>products[i]</code> consists of lowercase English letters.</li>
	<li><code>1 &lt;= searchWord.length &lt;= 1000</code></li>
	<li><code>searchWord</code> consists of lowercase English letters.</li>
</ul>

class Solution {
public:
    class Trie {
      public:
        Trie() {
            parent_ = nullptr;
            for (int i = 0; i < 26; i++) {
                children[i] = nullptr;
            }
        }
        Trie(const std::string& prefix, Trie* parent) {
            prefix_ = prefix;
            parent_ = parent;
            for (int i = 0; i < 26; i++) {
                children[i] = nullptr;
            }
        }
        std::string prefix_;
        Trie* parent_;
        Trie *children[26];
        std::set<std::string> suggestions;
    };

    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
        return suggestedProductsUsingTrie(products, searchWord);
    }

    void InsertAndKeepTop3(std::set<std::string>& suggestions, std::string word) {
        suggestions.insert(word);
        return;
        int count = 0;
        for (auto iter = suggestions.begin(); iter != suggestions.end(); ++iter) {
            if (++count > 3) {
                suggestions.erase(iter);
            }
        }
    }

    vector<vector<string>> suggestedProductsUsingTrie(vector<string>& products, string searchWord) {
        std::set<std::string> dict(products.begin(), products.end());
        // Return a list of lists of the suggested products after each character of searchWord is typed.
        Trie* root = new Trie;
        for (string& product : products) {
            Trie* node = root;
            std::string prefix;
            for (char ch : product) {
                prefix.append(1, ch);
                Trie* child_node = node->children[ch - 'a'];
                if (child_node == nullptr) {
                    child_node = new Trie(prefix, node);
                    node->children[ch - 'a'] = child_node;
                }
                node = child_node;
            }
            assert(node->prefix_ == product);
            InsertAndKeepTop3(node->suggestions, product);
            Trie* parent = node->parent_;
            while (parent != nullptr && parent->parent_ != nullptr) {
                InsertAndKeepTop3(parent->suggestions, product);
                parent = parent->parent_;
            }
        }

        std::vector<std::vector<std::string>> result;
        Trie* node = root;
        for (char ch : searchWord) {
            vector<string> suggestions; 
            if (node != nullptr) {
            node = node->children[ch - 'a'];    
            if (node != nullptr) {
                int count = 0;
                for (const string& s : node->suggestions) {
                    if (++count > 3) break;
                    suggestions.push_back(s);
                }
            }
            }
            result.push_back(suggestions);
        }
        return result;
    }
};
178510