<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 {
public:

    int dfs(vector<string>& s, string& t, int mask, unordered_map<int, int>& dp){
        int res = 1e9, a = 0;
        int t_mask = mask;
        vector<int> temp(26 ,0);
        
        if(dp[mask])return dp[mask];

        for(int i=0; i<t.size(); i++)if(mask & (1<<i))a++;
        if(a==t.size())return 0;

        for(int i=0;i<s.size();i++){
            fill(temp.begin(), temp.end(), 0);
            for(auto &_s: s[i])temp[_s - 'a']++;
            int match = 0;
            for(int j=0;j<t.size();j++){
                if(temp[t[j]-'a'] && !(mask & (1<<j))){
                    match++;
                    mask = mask | (1<<j);
                    temp[t[j]-'a']--;
                }
            }
            if(match)res = min(res, 1 + dfs(s, t, mask, dp));
            mask = t_mask;
        } 

        return dp[t_mask] = res;
    }

    int minStickers(vector<string>& stickers, string target) {

        unordered_map<int, int>dp;

        int ans = dfs(stickers, target, 0, dp);

        return ans<1e9?ans:-1;
    }
};
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