<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 solve(int i,int vis,string& target,vector<string>& stickers,vector<vector<int>>& dp)
    {
        int n=stickers.size();
        if(i==n) {
            for(int j=0;j<target.size();j++) if(!(vis & (1<<j))) return target.size()+1;
            return 0;
        }
        if(dp[i][vis]!=-1) return dp[i][vis];
        vector<int> f(26,0);
        for(int j=0;j<stickers[i].size();j++) f[stickers[i][j]-'a']++;

        int ans=target.size()+1;
        ans=min(ans,solve(i+1,vis,target,stickers,dp));
        int dummy =vis;
        int cnt1=0;
        for(int j=0;j<target.size();j++){
            if( (!(vis & (1<<j))) && f[target[j]-'a']>0 ){
                // vis[j]=1; 
                vis = vis | (1<<j);
                f[target[j]-'a']--; cnt1++;
            }
        }

        if(cnt1!=0) {
            ans=min(ans,1+solve(i,vis,target,stickers,dp));
        }
        return dp[i][dummy]=ans;

    }
    int minStickers(vector<string>& stickers, string target) {
        // vector<int> vis(target.size());
        // int vis=0;
        int n=stickers.size();
        int x = 1<<(15);
        vector<vector<int>> dp(n,vector<int>(x+1,-1));
        int ans= solve(0,0,target,stickers,dp);
        if(ans>target.size()) return -1;
        return ans;
    }
};
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