<p>Given an <code>m x n</code> <code>board</code>&nbsp;of characters and a list of strings <code>words</code>, return <em>all words on the board</em>.</p>

<p>Each word must be constructed from letters of sequentially adjacent cells, where <strong>adjacent cells</strong> are horizontally or vertically neighboring. The same letter cell may not be used more than once in a word.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/07/search1.jpg" style="width: 322px; height: 322px;" />
<pre>
<strong>Input:</strong> board = [[&quot;o&quot;,&quot;a&quot;,&quot;a&quot;,&quot;n&quot;],[&quot;e&quot;,&quot;t&quot;,&quot;a&quot;,&quot;e&quot;],[&quot;i&quot;,&quot;h&quot;,&quot;k&quot;,&quot;r&quot;],[&quot;i&quot;,&quot;f&quot;,&quot;l&quot;,&quot;v&quot;]], words = [&quot;oath&quot;,&quot;pea&quot;,&quot;eat&quot;,&quot;rain&quot;]
<strong>Output:</strong> [&quot;eat&quot;,&quot;oath&quot;]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/07/search2.jpg" style="width: 162px; height: 162px;" />
<pre>
<strong>Input:</strong> board = [[&quot;a&quot;,&quot;b&quot;],[&quot;c&quot;,&quot;d&quot;]], words = [&quot;abcb&quot;]
<strong>Output:</strong> []
</pre>

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

<ul>
	<li><code>m == board.length</code></li>
	<li><code>n == board[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 12</code></li>
	<li><code>board[i][j]</code> is a lowercase English letter.</li>
	<li><code>1 &lt;= words.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>1 &lt;= words[i].length &lt;= 10</code></li>
	<li><code>words[i]</code> consists of lowercase English letters.</li>
	<li>All the strings of <code>words</code> are unique.</li>
</ul>

class Solution {
public:
    void help(vector<vector<char>>&board,unordered_map<string,int>&mp,string &t,int i,int j,unordered_map<string,int>&store,int len){
        if(i>=board.size() || j>=board[0].size() || i<0 || j<0 || board[i][j]=='0'){return;}
        //if(store[t]==0){return;}
        if(t.size()>=len){return;}
        char temp1=board[i][j];
        t.push_back(board[i][j]);
        board[i][j]='0';
        mp[t]=1;
        help(board,mp,t,i+1,j,store,len);
        help(board,mp,t,i,j+1,store,len);
        help(board,mp,t,i-1,j,store,len);
        help(board,mp,t,i,j-1,store,len);
        board[i][j]=temp1;
        t.pop_back();
    }
    vector<string> findWords(vector<vector<char>>& board, vector<string>& words) {
        unordered_map<string,int>mp;
        unordered_map<string,int>store;
        int len=0;
        string g;
        for(int i=0;i<words.size();i++){
            g="";
            for(int j=0;j<words[i].size();j++){
                 g+=words[i][j];
                 store[g]=1;
            }
            len=max(len,(int)words[i].size());
        }
        string t="";
        store[t]=1;
        for(int i=0;i<board.size();i++){
            for(int j=0;j<board[0].size();j++){
                help(board,mp,t,i,j,store,len);
            }
        }
        vector<string>ans;
        for(auto x:words){
            if(mp[x]){
                ans.push_back(x);
            }
        }
        return ans;
    }
};
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