<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:
    struct TrieNode {
        TrieNode* childNode[26];
        bool wordEnd;
        TrieNode() {
            for(int i=0; i<26; i++) childNode[i] = NULL;
            wordEnd = false;
        }
    };

    int minExtraChar(string s, vector<string>& dictionary) {
        TrieNode* root = new TrieNode();
        buildTrie(root, dictionary);
        unordered_map<int, int> dp;
        findMinExtraChar(s, 0, root, dp);
        return dp[0];
    }

     int findMinExtraChar(const string& s, int index, TrieNode* root, unordered_map<int, int> &dp) {
        if (index == s.size()) {
            return 0;
        }
        if(dp[index]) return dp[index];
        int ans = findMinExtraChar(s, index+1, root, dp) + 1;
        TrieNode* current = root;
        for (int i = index; i < s.size(); i++) {
            if (!current->childNode[s[i] - 'a']) {
                break;
            }
            current = current->childNode[s[i] - 'a'];
            if (current->wordEnd) {
                ans = min(ans, dp[i+1]);
            }
        }

        return dp[index] = ans;
    }

    // int findMinExtraChar(const string& s, int index, TrieNode* root, TrieNode* node) {
    //     if (index == s.size()) {
    //         return 0;
    //     }

    //     int exclude = 1 + findMinExtraChar(s, index + 1, root, root);
    //     int include = INT_MAX;

    //     if (node->childNode[s[index] - 'a']) {
    //         TrieNode* nextNode = node->childNode[s[index] - 'a'];
    //         if (nextNode->wordEnd) {
    //             include = findMinExtraChar(s, index + 1, root, root);
    //         }
    //         include = min(include, findMinExtraChar(s, index + 1, root, nextNode));
    //     }

    //     return min(exclude, include);
    // }

    void buildTrie(TrieNode *root, vector<string> &dictionary) {
        for(int i=0; i<dictionary.size(); i++) {
            TrieNode *current = root;
            for(int j=0; j<dictionary[i].size(); j++){
                if(!current->childNode[dictionary[i][j] - 'a']) {
                    current->childNode[dictionary[i][j] - 'a'] = new TrieNode();
                }
                current = current->childNode[dictionary[i][j] - 'a'];
            }
            current->wordEnd = true;
        }
    }
};
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