<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:
    map<string, int> dp;
    int dfs(vector<map<char, int>> &stickersMap, string target) {
        if (dp.find(target) != dp.end()) {
            return dp[target];
        }
        if(target.empty()) {
            return 0;
        }
        int len = stickersMap.size(), ans = INT_MAX - 1;
        for (int i = 0; i < len; i++) {
            if (stickersMap[i].find(target[0]) != stickersMap[i].end()) {
                map<char, int> tempStickersMapAtI = stickersMap[i];
                string newTarget;
                for (char ch : target) {
                    if (stickersMap[i].find(ch) != stickersMap[i].end() && stickersMap[i][ch] != 0) {
                        stickersMap[i][ch]--;
                        continue;
                    }
                    newTarget += ch;
                }
                stickersMap[i] = tempStickersMapAtI;
                ans = min(dfs(stickersMap, newTarget), ans);
            }
        }
        ans++;
        return dp[target] = ans;
    }

    int minStickers(vector<string>& stickers, string target) {
        int len = stickers.size();
        vector<map<char, int>> stickersMap(len);
        for (int i = 0; i < len; i++) {
            for (char ch : stickers[i]) {
                stickersMap[i][ch]++;
            }
        }

        int ans = dfs(stickersMap, target);
        return (ans == INT_MAX ? -1 : ans);
    }
};
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