<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:
    unordered_map<string, int>mp;
    int minStickers(vector<string>& stickers, string target) {
        int result = traverse(stickers, 0, target);
        return result == INT_MAX ? -1 : result;
    }


    int traverse(vector<string> &stickers, int index, string& target)
    {
        if(target == "")
            return 0;
        
        if(index >= stickers.size())
            return INT_MAX;

        string key = target + "_" + to_string(index);
        
        if(mp.find(key) != mp.end())
            return mp[key];
        
        int result = traverse(stickers, index + 1, target);

        string currentSticker = stickers[index];
        string newTarget = target;
        int flag = 0;

        for(auto &ch: currentSticker)
        {
            int pos = newTarget.find(ch);
            if (pos != -1) {
                newTarget.erase(pos, 1);
                flag = 1;
            }
            //cout<<currentSticker<<" "<<target<<" "<<newTarget<<endl;
        }
            
        if(flag)
        {
            int temp = traverse(stickers, index, newTarget);
            if(temp != INT_MAX)
                temp++;
            result = min(result, temp);   
        }

        return mp[key] = result;
    }
};
179026