<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 dp[50][(1<<15)];
    int func(int ind,int mask,vector<string>&vs,string &target,int m){
        if(mask == (1<<m)-1) return 0;
        if(ind == vs.size()) return 1e9;
        if(dp[ind][mask]!=-1) return dp[ind][mask];
        int ans = 1e9;
        string s1 = vs[ind];
        int newmask = 0;
        vector<int>fre1(26);
        for(int i = 0;i<s1.size();i++){
            fre1[s1[i]-'a']++;
        }
        for(int i = 0;i<m;i++){
            if(fre1[target[i]-'a'] && (mask & (1<<i))==0){
                fre1[target[i]-'a']--;
                newmask|=(1<<i);
            }
        }
        if(newmask != 0){
            ans = min(ans,1+func(ind,mask|newmask,vs,target,m));
        }
        ans = min(ans,func(ind+1,mask,vs,target,m));
        return dp[ind][mask] = ans;
    }
    int minStickers(vector<string>& stickers, string target) {
        memset(dp,-1,sizeof(dp));
        int ans= func(0,0,stickers,target,target.size());
        return (ans == 1e9) ? -1:ans;
    }
};
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