<p>A <strong>transformation sequence</strong> from word <code>beginWord</code> to word <code>endWord</code> using a dictionary <code>wordList</code> is a sequence of words <code>beginWord -&gt; s<sub>1</sub> -&gt; s<sub>2</sub> -&gt; ... -&gt; s<sub>k</sub></code> such that:</p>

<ul>
	<li>Every adjacent pair of words differs by a single letter.</li>
	<li>Every <code>s<sub>i</sub></code> for <code>1 &lt;= i &lt;= k</code> is in <code>wordList</code>. Note that <code>beginWord</code> does not need to be in <code>wordList</code>.</li>
	<li><code>s<sub>k</sub> == endWord</code></li>
</ul>

<p>Given two words, <code>beginWord</code> and <code>endWord</code>, and a dictionary <code>wordList</code>, return <em>all the <strong>shortest transformation sequences</strong> from</em> <code>beginWord</code> <em>to</em> <code>endWord</code><em>, or an empty list if no such sequence exists. Each sequence should be returned as a list of the words </em><code>[beginWord, s<sub>1</sub>, s<sub>2</sub>, ..., s<sub>k</sub>]</code>.</p>

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

<pre>
<strong>Input:</strong> beginWord = &quot;hit&quot;, endWord = &quot;cog&quot;, wordList = [&quot;hot&quot;,&quot;dot&quot;,&quot;dog&quot;,&quot;lot&quot;,&quot;log&quot;,&quot;cog&quot;]
<strong>Output:</strong> [[&quot;hit&quot;,&quot;hot&quot;,&quot;dot&quot;,&quot;dog&quot;,&quot;cog&quot;],[&quot;hit&quot;,&quot;hot&quot;,&quot;lot&quot;,&quot;log&quot;,&quot;cog&quot;]]
<strong>Explanation:</strong>&nbsp;There are 2 shortest transformation sequences:
&quot;hit&quot; -&gt; &quot;hot&quot; -&gt; &quot;dot&quot; -&gt; &quot;dog&quot; -&gt; &quot;cog&quot;
&quot;hit&quot; -&gt; &quot;hot&quot; -&gt; &quot;lot&quot; -&gt; &quot;log&quot; -&gt; &quot;cog&quot;
</pre>

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

<pre>
<strong>Input:</strong> beginWord = &quot;hit&quot;, endWord = &quot;cog&quot;, wordList = [&quot;hot&quot;,&quot;dot&quot;,&quot;dog&quot;,&quot;lot&quot;,&quot;log&quot;]
<strong>Output:</strong> []
<strong>Explanation:</strong> The endWord &quot;cog&quot; is not in wordList, therefore there is no valid transformation sequence.
</pre>

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

<ul>
	<li><code>1 &lt;= beginWord.length &lt;= 5</code></li>
	<li><code>endWord.length == beginWord.length</code></li>
	<li><code>1 &lt;= wordList.length &lt;= 500</code></li>
	<li><code>wordList[i].length == beginWord.length</code></li>
	<li><code>beginWord</code>, <code>endWord</code>, and <code>wordList[i]</code> consist of lowercase English letters.</li>
	<li><code>beginWord != endWord</code></li>
	<li>All the words in <code>wordList</code> are <strong>unique</strong>.</li>
	<li>The <strong>sum</strong> of all shortest transformation sequences does not exceed <code>10<sup>5</sup></code>.</li>
</ul>

class Solution {
public:
    vector<vector<string>> findLadders(string beginWord, string endWord, vector<string>& wordList) {
        int is_begin = 0, end_index = -1, begin_index = -1;
        vector<vector<string>> re;
        for (int i = 0;i<wordList.size();i++){
            if (wordList[i]==beginWord) is_begin=1;
            if (wordList[i]==endWord) end_index = i;
            if (wordList[i]==beginWord) begin_index = i;
        }
        if (end_index==-1) return re;
        if (is_begin==0) wordList.emplace_back(beginWord);
        if (is_begin==0) begin_index = wordList.size()-1;
        int **adj = new int*[wordList.size()], *level = new int[wordList.size()](), *degree = new int[wordList.size()]();
        fill_n(level,wordList.size(),-1);
        for (int i = 0;i<wordList.size();i++){
            adj[i] = new int[wordList.size()];
            fill_n(adj[i],wordList.size(),-1);
        }
        for (int i = 0;i<wordList.size();i++){
            for (int j = i+1;j<wordList.size();j++){
                int status = 0;
                for (int z = 0;z<wordList[i].size();z++){
                    if (wordList[i][z]!=wordList[j][z]) status++;
                }
                if (status==1){
                    adj[i][degree[i]] = j;
                    degree[i]++;
                    adj[j][degree[j]] = i;
                    degree[j]++;
                }
            }
        }
        int *status = new int[wordList.size()](), is_con = 0;
        queue<int> need_search;
        need_search.push(begin_index);
        status[begin_index] = 1;
        level[begin_index] = 0;
        while(need_search.size()>0){
            int cur = need_search.front();
            int neigh = 0;
            while(adj[cur][neigh]!=-1){
                if (status[adj[cur][neigh]]==0){
                    need_search.push(adj[cur][neigh]);
                    status[adj[cur][neigh]] = 1;
                    level[adj[cur][neigh]] = level[cur]+1;
                }
                if (adj[cur][neigh]==end_index){
                    is_con = 1;
                    break;
                }
                neigh++;
            }
            need_search.pop();
        }
        if (is_con==0) return re;
        stack<int> need_scan;
        need_scan.push(end_index);
        vector<string> add(level[end_index]+1,wordList[end_index]);
        while(need_scan.size()>0){
            int cur = need_scan.top();
            // if (level[cur]==level[end_index]-1){
            //     vector<string> tmp;
            //     add.swap(tmp);
            //     add.emplace(add.begin(),endWord);
            // }
            add[level[cur]] = wordList[cur];
//            cout<<wordList[cur]<<endl;
            if (level[cur]==0){
                re.emplace_back(add);
            }
            need_scan.pop();
            int neigh = 0;
            while(adj[cur][neigh]!=-1){
                if (level[adj[cur][neigh]]==level[cur]-1){
                    need_scan.push(adj[cur][neigh]);
 //                   cout<<adj[cur][neigh]<<endl;
                }
                neigh++;
            }
        }
        return re;
    }
};
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