<p>We are given <code>n</code> different types of <code>stickers</code>. Each sticker has a lowercase English word on it.</p>

<p>You would like to spell out the given string <code>target</code> by cutting individual letters from your collection of stickers and rearranging them. You can use each sticker more than once if you want, and you have infinite quantities of each sticker.</p>

<p>Return <em>the minimum number of stickers that you need to spell out </em><code>target</code>. If the task is impossible, return <code>-1</code>.</p>

<p><strong>Note:</strong> In all test cases, all words were chosen randomly from the <code>1000</code> most common US English words, and <code>target</code> was chosen as a concatenation of two random words.</p>

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

<pre>
<strong>Input:</strong> stickers = [&quot;with&quot;,&quot;example&quot;,&quot;science&quot;], target = &quot;thehat&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong>
We can use 2 &quot;with&quot; stickers, and 1 &quot;example&quot; sticker.
After cutting and rearrange the letters of those stickers, we can form the target &quot;thehat&quot;.
Also, this is the minimum number of stickers necessary to form the target string.
</pre>

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

<pre>
<strong>Input:</strong> stickers = [&quot;notice&quot;,&quot;possible&quot;], target = &quot;basicbasic&quot;
<strong>Output:</strong> -1
Explanation:
We cannot form the target &quot;basicbasic&quot; from cutting letters from the given stickers.
</pre>

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

<ul>
	<li><code>n == stickers.length</code></li>
	<li><code>1 &lt;= n &lt;= 50</code></li>
	<li><code>1 &lt;= stickers[i].length &lt;= 10</code></li>
	<li><code>1 &lt;= target.length &lt;= 15</code></li>
	<li><code>stickers[i]</code> and <code>target</code> consist of lowercase English letters.</li>
</ul>

class Solution {
    int n;
    unordered_map<char,vector<int>>m;
    int u;
    int dp[100001];
    int solve(int mask,vector<string>&st){
        if(m.empty())return 0;
        if(dp[mask]!=-1)return dp[mask];
        int ans=10000;
        for(auto &s:st){
            int f=0;
            vector<pair<char,int>>v;
            int temp=mask;
            for(auto &c:s){
                if(m.count(c)){
                    v.push_back({c,m[c].back()});
                    temp|=1ll<<m[c].back();
                    m[c].pop_back();
                    if(m[c].size()==0){
                        m.erase(c);
                    }
                    f=1;
                }
            }
            reverse(v.begin(),v.end());
            if(f==1)
            ans=min(ans,1+solve(temp,st));
            for(auto i:v){
                m[i.first].push_back(i.second);
            }
        }
        return dp[mask]=ans;
    }
public:
    int minStickers(vector<string>& st, string tar) {
        u=tar.size();
        memset(dp,-1,sizeof(dp));
        for(int i=0;i<tar.size();i++){
            m[tar[i]].push_back(i);
        }
        int n=st.size();
        int ans=solve(0,st);
        if(ans>100)return -1;
        return ans;
    }
};
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