<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 helper(vector<vector<int>> &arr, string target, unordered_map<string,int> &dp){
        if(target == ""){
            return 0;
        }
        if(dp.find(target) != dp.end()){
            return dp[target];
        }
        int ans = INT_MAX;
        for(int i=0;i<arr.size();i++){
            vector<int> temp = arr[i];
            string curr = "";
            for(int j=0;j<target.length();j++){
                if(temp[target[j]-'a'] > 0){
                    temp[target[j]-'a']--;
                }
                else{
                    curr.push_back(target[j]);
                }
            }
            if(curr == target){
                continue;
            }
            ans = min(ans,1+helper(arr,curr,dp));
        }
        dp[target] = ans;
        return ans;
    }
    
    int minStickers(vector<string>& stickers, string target) {
        int n = stickers.size();
        vector<vector<int>> arr(n,vector<int>(26,0));
        vector<bool> all(26,false);
        for(int i=0;i<n;i++){
            string curr = stickers[i];
            for(int j=0;j<curr.length();j++){
                arr[i][curr[j]-'a']++;
                all[curr[j]-'a'] = true;
            }
        }
        for(int i=0;i<target.length();i++){
            if(!all[target[i]-'a']){
                return -1;
            }
        }
        unordered_map<string,int> dp;
        int ans = helper(arr,target,dp);
        return ans;
    }
};
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