<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>

struct Node {
    bool isWord;
    string word;
    vector<Node*> children;
    Node() : isWord(false), word(""), children(26, NULL) {}
};

class Trie {
public:
    Trie() {
        root = new Node();
    }

    void insert(const string& word) {
        Node* curr = root;
        for (char c : word) {
            size_t idx = c - 'a';
            if (!curr->children[idx])
                curr->children[idx] = new Node();
            curr = curr->children[idx];
        }
        curr->isWord = true;
        curr->word = word;
    }
    
    string getWordRoot(const string& word) {
        Node* curr = root;
        for (char c : word) {
            size_t idx = c - 'a';
            if (curr->isWord) return curr->word;
            if (!curr->children[idx]) return word;
            curr = curr->children[idx];
        }
        return word;
    }

private:
    Node* root;
};

class Solution {
public:
    string replaceWords(vector<string>& dictionary, string sentence) {
        Trie trie;
        for (const string& root : dictionary) {
            trie.insert(root);
        }
        string word, ans = "";
        istringstream iss(sentence);
        while (iss >> word) {
            ans += trie.getWordRoot(word) + " ";
        }
        // ans.pop_back();
        return ans.substr(0, ans.length() - 1);
    }
};
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