<p>In English, we have a concept called <strong>root</strong>, which can be followed by some other word to form another longer word - let&#39;s call this word <strong>derivative</strong>. For example, when the <strong>root</strong> <code>&quot;help&quot;</code> is followed by the word <code>&quot;ful&quot;</code>, we can form a derivative <code>&quot;helpful&quot;</code>.</p>

<p>Given a <code>dictionary</code> consisting of many <strong>roots</strong> and a <code>sentence</code> consisting of words separated by spaces, replace all the derivatives in the sentence with the <strong>root</strong> forming it. If a derivative can be replaced by more than one <strong>root</strong>, replace it with the <strong>root</strong> that has <strong>the shortest length</strong>.</p>

<p>Return <em>the <code>sentence</code></em> after the replacement.</p>

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

<pre>
<strong>Input:</strong> dictionary = [&quot;cat&quot;,&quot;bat&quot;,&quot;rat&quot;], sentence = &quot;the cattle was rattled by the battery&quot;
<strong>Output:</strong> &quot;the cat was rat by the bat&quot;
</pre>

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

<pre>
<strong>Input:</strong> dictionary = [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;], sentence = &quot;aadsfasf absbs bbab cadsfafs&quot;
<strong>Output:</strong> &quot;a a b c&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= dictionary.length &lt;= 1000</code></li>
	<li><code>1 &lt;= dictionary[i].length &lt;= 100</code></li>
	<li><code>dictionary[i]</code> consists of only lower-case letters.</li>
	<li><code>1 &lt;= sentence.length &lt;= 10<sup>6</sup></code></li>
	<li><code>sentence</code> consists of only lower-case letters and spaces.</li>
	<li>The number of words in <code>sentence</code> is in the range <code>[1, 1000]</code></li>
	<li>The length of each word in <code>sentence</code> is in the range <code>[1, 1000]</code></li>
	<li>Every two consecutive words in <code>sentence</code> will be separated by exactly one space.</li>
	<li><code>sentence</code> does not have leading or trailing spaces.</li>
</ul>

class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        buildTree(dictionary);

        std::string result;
        std::stringstream sstr(sentence);
        std::string word;
        while (sstr >> word) {
            result += shortestRoot(word) + " ";
        }
        result.pop_back();
        return result;
    }

private:
    std::string shortestRoot(std::string &word) {
        TrieNode *node = m_root;

        int len = static_cast<int>(word.size());
        for (int index = 0; index < len; ++index) {
            if (!node->isContain(word[index])) {
                return word;
            }
            node = node->get(word[index]);
            if (node && node->isEnd()) {
                return word.substr(0, index + 1);
            }
        }
        return word;
    }
    void buildTree(std::vector<std::string> &dict) {
        m_root = new TrieNode();
        
        for (const auto &str : dict) {
            TrieNode *node = m_root;
            for (const auto &c : str) {
                node->put(c);
                node = node->get(c);
            }
            node->setEnd(true);
        }
    }
    
    class TrieNode {
    public:
        TrieNode() {
            m_data.resize(26, nullptr);
            m_isEnd = false;
        }

        void put(const char c) {
            if (!isContain(c)) {
                m_data[c - 'a'] = new TrieNode();
            }
        }

        TrieNode *get(const char c) {
            return isContain(c) ? m_data[c - 'a'] : nullptr;
        }

        bool isContain(const char c) {
            return m_data[c - 'a'];
        }

        void setEnd(bool isEnd) {
            m_isEnd = isEnd;
        }

        bool isEnd() { return m_isEnd; }
    private:
        std::vector<TrieNode*> m_data;
        bool m_isEnd;
    };
    TrieNode *m_root;
};
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