<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:
//     #include<bits/stdc++.h>
// using namespace std;

int node,trie[300001][26],cnt[300001];
map<int, string>vec;
void insert(vector<string>&words)
{
    for(int i=0;i<words.size();i++)
    {
        int val=0,val1;
        for(auto itr:words[i])
        {
            val1=itr-'a';
            if(!trie[val][val1])
            {
                trie[val][val1]=++node;
            }
            val=trie[val][val1];
        }
        cnt[val]++;
        vec.insert({val,words[i]});
    }
}
void find(int x,int y,int n,int m,vector<vector<char>>&board,int pos,vector<string>&ans)
{
    if(cnt[pos]>0)
    {
        ans.push_back(vec[pos]);
        cnt[pos]=0;
    }
    if(x<0 || y<0 || x>=n || y>=m || board[x][y]=='#')
    {
        return;
    }
    int val=board[x][y]-'a';
    if(!trie[pos][val])
    {
        return;
    }
    char ch=board[x][y];
    board[x][y]='#';
    find(x+1,y,n,m,board,trie[pos][val],ans);
    find(x-1,y,n,m,board,trie[pos][val],ans);
    find(x,y+1,n,m,board,trie[pos][val],ans);
    find(x,y-1,n,m,board,trie[pos][val],ans);
    board[x][y]=ch;
}
vector<string> findWords(vector<vector<char>> &board, vector<string> &words) {
    int n=board.size(),m=board[0].size();
    memset(trie,0,sizeof(trie));
    memset(cnt,0,sizeof(cnt));
    vec.clear();
    node=0;
    vector<string>ans;
    insert(words);
    for(int i=0;i<n;i++)
    {
        for(int j=0;j<m;j++)
        {
            find(i,j,n,m,board,0,ans);
        }
    }
    sort(ans.begin(),ans.end());
    return ans;
}
};
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