<p>You are given a <strong>0-indexed</strong> string <code>s</code> and a dictionary of words <code>dictionary</code>. You have to break <code>s</code> into one or more <strong>non-overlapping</strong> substrings such that each substring is present in <code>dictionary</code>. There may be some <strong>extra characters</strong> in <code>s</code> which are not present in any of the substrings.</p>

<p>Return <em>the <strong>minimum</strong> number of extra characters left over if you break up </em><code>s</code><em> optimally.</em></p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;leetscode&quot;, dictionary = [&quot;leet&quot;,&quot;code&quot;,&quot;leetcode&quot;]
<strong>Output:</strong> 1
<strong>Explanation:</strong> We can break s in two substrings: &quot;leet&quot; from index 0 to 3 and &quot;code&quot; from index 5 to 8. There is only 1 unused character (at index 4), so we return 1.

</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;sayhelloworld&quot;, dictionary = [&quot;hello&quot;,&quot;world&quot;]
<strong>Output:</strong> 3
<strong>Explanation:</strong> We can break s in two substrings: &quot;hello&quot; from index 3 to 7 and &quot;world&quot; from index 8 to 12. The characters at indices 0, 1, 2 are not used in any substring and thus are considered as extra characters. Hence, we return 3.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 50</code></li>
	<li><code>1 &lt;= dictionary.length &lt;= 50</code></li>
	<li><code>1 &lt;= dictionary[i].length &lt;= 50</code></li>
	<li><code>dictionary[i]</code>&nbsp;and <code>s</code> consists of only lowercase English letters</li>
	<li><code>dictionary</code> contains distinct words</li>
</ul>

class Solution {
public:
    string getStr(string s, int i, int j){
        string p = "";
        for(int k = i; k <= j; k++) p += s[k];
        
        return p;
    }
    int solve(string s, unordered_set<string>&hs, int ind, int dp[]){
        if(ind == s.length()) return 0;
        if(dp[ind] != -1) return dp[ind];
        
        int ret  = 1 + solve(s, hs, ind + 1, dp);
        
        for(int i = ind; i < s.length(); i++){
            string ns = getStr(s, ind, i);
            if(hs.find(ns) != hs.end()){
                ret = min(ret, solve(s, hs, i + 1, dp));
            }
        }
        return dp[ind] = ret;
    }
    int minExtraChar(string s, vector<string>& dict) {
        int dp[s.length()];
        for(int i = 0; i < s.length(); i++) dp[i] = -1;
        unordered_set<string>hs;
        for(auto itr: dict)hs.insert(itr);
        return solve(s, hs, 0, dp);
    }
};


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