<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 TrieNode
{
public:
    TrieNode* children[26];
    bool is_word;
    TrieNode();
    void insert(const std::string& s);
    void traverse(const std::string& prefix, std::string cur, int& k, std::vector<std::string>& res);
    TrieNode* find(const std::string& s);
};

TrieNode::TrieNode()
{
    for (int i = 0; i < 26; i ++)
    {
        children[i] = NULL;
        is_word = false;
    }
};

TrieNode* TrieNode::find(const std::string& s)
{
    TrieNode* cur = this;
    for (int i = 0; i < s.length(); i ++)
    {
        int ind = s[i] - 'a';
        if (cur->children[ind] == NULL)
        {
            return NULL;
        }
        else
        {
            cur = cur->children[ind];
        }
    }
    return cur;
}

void TrieNode::insert(const std::string& s)
{
    TrieNode* cur = this;
    for (int i = 0; i < s.length(); i ++)
    {
        int ind = s[i] - 'a';
        if (cur->children[ind] == NULL)
        {
            cur->children[ind] = new TrieNode();
        }
        cur = cur->children[ind];
    }
    cur->is_word = true;
    
};

void TrieNode::traverse(const std::string& prefix, std::string cur, int& k, std::vector<std::string>& res)
{
    if (k == 0)
        return ;
    
    if (is_word)
    {
        res.push_back(prefix + cur);
        k --;
    }

    for (int i = 0; i < 26; i ++)
    {
        if (children[i] != NULL)
        {
            children[i]->traverse(prefix, cur + (char)('a' + i), k, res);
        }
    }
}

class Solution {
public:
    vector<vector<string>> suggestedProducts(vector<string>& products, string searchWord) {
        TrieNode* root = new TrieNode();
        for (int i = 0; i < products.size(); i ++)
        {
            root->insert(products[i]);
        }

        std::vector<std::vector<std::string>> ret(searchWord.length());
        for (int i = 0; i < searchWord.length(); i ++)
        {
            int k = 3;
            std::string prefix = searchWord.substr(0, i + 1);
            TrieNode* start = root->find(prefix);
            if (start != NULL)
                start->traverse(prefix, std::string(), k, ret[i]);
        }
        return ret;
    }
};
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