<p>Given a string <code>s</code> and a dictionary of strings <code>wordDict</code>, add spaces in <code>s</code> to construct a sentence where each word is a valid dictionary word. Return all such possible sentences in <strong>any order</strong>.</p>

<p><strong>Note</strong> that the same word in the dictionary may be reused multiple times in the segmentation.</p>

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

<pre>
<strong>Input:</strong> s = &quot;catsanddog&quot;, wordDict = [&quot;cat&quot;,&quot;cats&quot;,&quot;and&quot;,&quot;sand&quot;,&quot;dog&quot;]
<strong>Output:</strong> [&quot;cats and dog&quot;,&quot;cat sand dog&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;pineapplepenapple&quot;, wordDict = [&quot;apple&quot;,&quot;pen&quot;,&quot;applepen&quot;,&quot;pine&quot;,&quot;pineapple&quot;]
<strong>Output:</strong> [&quot;pine apple pen apple&quot;,&quot;pineapple pen apple&quot;,&quot;pine applepen apple&quot;]
<strong>Explanation:</strong> Note that you are allowed to reuse a dictionary word.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;catsandog&quot;, wordDict = [&quot;cats&quot;,&quot;dog&quot;,&quot;sand&quot;,&quot;and&quot;,&quot;cat&quot;]
<strong>Output:</strong> []
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 20</code></li>
	<li><code>1 &lt;= wordDict.length &lt;= 1000</code></li>
	<li><code>1 &lt;= wordDict[i].length &lt;= 10</code></li>
	<li><code>s</code> and <code>wordDict[i]</code> consist of only lowercase English letters.</li>
	<li>All the strings of <code>wordDict</code> are <strong>unique</strong>.</li>
	<li>Input is generated in a way that the length of the answer doesn&#39;t exceed&nbsp;10<sup>5</sup>.</li>
</ul>

class Solution {
public:
    vector<string> v;
    vector<string> current;
    class TrieNode{
        public:
        bool isWord;
        TrieNode* children[26];
        TrieNode(){
            isWord = false;
            for(int i = 0;i<26;++i) children[i] = NULL;
        }
        void insert(TrieNode* root,string s){
            TrieNode* curr = root;
            for(int i =0 ;i<s.length();++i){
                if(curr->children[s[i]-'a']==NULL){
                    curr->children[s[i]-'a'] = new TrieNode();
                }
                curr = curr->children[s[i]-'a'];
            }
            curr->isWord = true;
        }
    };
    void rec(int i,string& s,TrieNode* root){
        if(i==s.length()){
            string ans = "";
            for(auto curr : current){
                ans += curr+" ";
            }
            ans.pop_back();
            v.push_back(ans);
            return;
        }
        TrieNode* curr = root;
        string temp = "";
        while(i<s.length()){
            if(curr->children[s[i]-'a']==NULL) return;
            temp+=s[i];
            curr = curr->children[s[i]-'a'];
            i++;
            if(curr->isWord){
                current.push_back(temp);
                rec(i,s,root);
                current.pop_back();
            }
        }
    }
    vector<string> wordBreak(string s, vector<string>& wordDict) {
        TrieNode* root = new TrieNode();
        for(auto word : wordDict){
            root->insert(root,word);
        }
        rec(0,s,root);
        return v;
    }
};
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