<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 {
private:
    struct TrieNode {
        int val;
        TrieNode* children[26] = {nullptr};

        TrieNode():val(0) {
            for (int i=0; i<26; i++) {
                children[i] = nullptr;
            }
        }
    };    

public:
    class Trie {
        TrieNode* root;
        public: // 必须声明否则不能用
        Trie() {
            root = new TrieNode();
        }

        void put(string word) {
            root = put(root, word, 0);
        }

        TrieNode* put(TrieNode* node, string word, int start) {
            if (node == nullptr) {
                node = new TrieNode();
            }
            if (start == word.size()) {
                node->val++;
                // cout<<1<<endl;
                return node;
            }

            char c = word[start];
            int ind = c-'a';
            // if (node->children[ind] == nullptr) {
            //     node->children[ind] = new TrieNode();
            // }
            node->children[ind]= put(node->children[ind], word, start+1);
            
            // cout<<c<<endl;
            // cout<<node->val<<endl;

            
            return node;
        }

        string shortPrefix(string word) {
            string res;
            TrieNode* node = root;
            for (char& c:word) {
                int ind = c-'a';
                res.push_back(c);
                // cout<< res<<endl;
                if (node->children[ind] == nullptr) {
                    // cout<<1<<endl;
                    node->children[ind] = new TrieNode();
                }
                if (node->children[ind]->val > 0) {
                    // cout<< res<<endl;
                    return res;
                } else {
                    node = node->children[ind];
                }
            }
            return res;
        }
    };

    string replaceWords(vector<string>& dictionary, string sentence) {
        Trie* root = new Trie();
        for (string& s:dictionary) {
            root->put(s);
        }
        string res, curr;
        for (char& c:sentence) {
            if (c==' ') {
                res += root->shortPrefix(curr);
                res.push_back(' ');
                curr = "";
            } else {
                curr.push_back(c);
            }
        }
        res += root->shortPrefix(curr);
        // res.pop_back();
        return res;
    }
};
322837