<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:
void search(string s,vector<string> curr, string A,map<string,vector<string>>& prev, vector<vector<string>>& ans)
{
    curr.push_back(s);
    if(s == A)
    {
        ans.push_back(curr);
        return;
    }
    
    for(auto pre: prev[s])
    {
        search(pre,curr,A,prev,ans);
    }
    curr.pop_back();
    
}

    vector<vector<string>> findLadders(string A, string B, vector<string>& C) {
        
         queue<string> q;
    q.push(A);
set<string> s;
    for(int i =0;i<C.size();i++)
    {
        s.insert(C[i]);
    }
    //s.insert(B);
    
map<string,vector<string>> prev;
map<string,int> dist;
    
    int steps = 1,f = 0;
    while(!q.empty() && f == 0)
    {
        int siz= q.size();
        
        while(siz--)
        {
            string top = q.front();
            q.pop();
            
            if(top == B)
            {
                f =1;
                break;
            }
                
            
            for(int i= 0;i<top.size();i++)
            {
                for(char ch = 'a';ch<='z';ch++)
                {
                    string adj = top;
                    if(ch == top[i])
                        continue;
                    
                    adj[i] = ch;
                    if(s.find(adj) != s.end())
                    {
                        //s.erase(adj);
                        if(prev.find(adj) == prev.end())
                        {
                            q.push(adj);
                            dist[adj] = steps+1;
                            prev[adj].push_back(top);
                        }
                        else if(steps +1 <= dist[adj])
                        {
                            prev[adj].push_back(top);
                        }
                    }
                }
            }
        }
        steps++;
        
    }

   

    vector<vector<string>> ans;
    vector<string> curr;
    search(B,curr,A,prev,ans);
    
    for(auto &v: ans)
    {
        reverse(v.begin(),v.end());
    }
    
    return ans;
    }
};
15000