Replace Words
<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>
Trie; Array; Hash Table; String
type Trie struct {
	children [26]*Trie
	ref      int
}

func newTrie() *Trie {
	return &Trie{ref: -1}
}

func (this *Trie) insert(w string, i int) {
	node := this
	for _, c := range w {
		idx := c - 'a'
		if node.children[idx] == nil {
			node.children[idx] = newTrie()
		}
		node = node.children[idx]
	}
	node.ref = i
}

func (this *Trie) search(w string) int {
	node := this
	for _, c := range w {
		idx := c - 'a'
		if node.children[idx] == nil {
			return -1
		}
		node = node.children[idx]
		if node.ref != -1 {
			return node.ref
		}
	}
	return -1
}

func replaceWords(dictionary []string, sentence string) string {
	trie := newTrie()
	for i, w := range dictionary {
		trie.insert(w, i)
	}
	ans := strings.Builder{}
	for _, w := range strings.Split(sentence, " ") {
		if idx := trie.search(w); idx != -1 {
			ans.WriteString(dictionary[idx])
		} else {
			ans.WriteString(w)
		}
		ans.WriteByte(' ')
	}
	return ans.String()[:ans.Len()-1]
}