<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>the <strong>number of words</strong> in the <strong>shortest transformation sequence</strong> from</em> <code>beginWord</code> <em>to</em> <code>endWord</code><em>, or </em><code>0</code><em> if no such sequence exists.</em></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> 5
<strong>Explanation:</strong> One shortest transformation sequence is &quot;hit&quot; -&gt; &quot;hot&quot; -&gt; &quot;dot&quot; -&gt; &quot;dog&quot; -&gt; cog&quot;, which is 5 words long.
</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> 0
<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;= 10</code></li>
	<li><code>endWord.length == beginWord.length</code></li>
	<li><code>1 &lt;= wordList.length &lt;= 5000</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>
</ul>

class Solution {
public:
    int ladderLength(string beginWord, string endWord, vector<string>& wordList) {
        map<string,vector<string>>mp;
        
        for(int i=0;i<wordList.size();i++){
            int c=0;
            for(int j=0;j<wordList[i].size();j++){
                if(beginWord[j]!=wordList[i][j])
                c++;
                if(c>1)
                break;
            }
            if(c==1){
                mp[beginWord].push_back(wordList[i]);
            }
          }

            for(int i=0;i<wordList.size();i++){
                string start = wordList[i];
                int c=0;
                for(int j=0;j<wordList.size();j++){
                    if(i==j)
                    continue;
                    int c=0;
                    for(int k=0;k<wordList[j].size();k++){
                        if(start[k]!=wordList[j][k])
                        c++;

                        if(c>1)
                        break;
                    }
                    if(c==1)
                    mp[start].push_back(wordList[j]);
                }
            }

            queue<string>q;
            q.push(beginWord);
            set<string>vis;
            vis.insert(beginWord);
            int ans=0,cur=0;

            while(!q.empty()){
                int sz= q.size();
                cur++;
                for(int i=0;i<sz;i++){
                    string node = q.front();
                    q.pop();
                    vis.insert(node);
                    if(node==endWord){
                        ans=cur;
                        return ans;
                    }
                    for(auto ch:mp[node]){
                        if(vis.find(ch)==vis.end()){
                            q.push(ch);
                        }
                    }
                }
            }
        return ans;
    }
};
58375