<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 minStickers(vector<string>& st, string tgt) {
        map<int, int> t_fr;
        vector<map<int, int>> s_fr;
        queue<map<int, int>> q;
        set<map<int, int>> vis;
        for (auto it : tgt) {
            t_fr[it]++;
        }
        for (auto it : st) {
            map<int, int> c_freq;
            for (auto itr : it) {
                c_freq[itr]++;
            }
            s_fr.push_back(c_freq);
        }
        int lvl = 0;
        q.push(t_fr);
        while (!q.empty()) {
            int qs = q.size();
            while (qs--) {
                auto cr = q.front();
                q.pop();
                if (vis.count(cr))
                    continue;
                if (cr.size() == 0)
                    return lvl;

                for (auto it : s_fr) {
                    map<int, int> n_freq = cr;
                    int fkey = n_freq.begin()->first;
                    if (!it.count(fkey))
                        continue;
                    for (auto itr : cr) {
                        if (it.count(itr.first)) {
                            n_freq[itr.first] -= it[itr.first];
                            if (n_freq[itr.first] <= 0)
                                n_freq.erase(itr.first);
                        }
                    }
                    if (!vis.count(n_freq))
                        q.push(n_freq);
                }
                vis.insert(cr);
            }
            lvl++;
        }
        return -1;
    }
};
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