<p>Given a string <code>s</code> and a dictionary of strings <code>wordDict</code>, return <code>true</code> if <code>s</code> can be segmented into a space-separated sequence of one or more dictionary words.</p>

<p><strong>Note</strong> that the same word in the dictionary may be reused multiple times in the segmentation.</p>

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

<pre>
<strong>Input:</strong> s = &quot;leetcode&quot;, wordDict = [&quot;leet&quot;,&quot;code&quot;]
<strong>Output:</strong> true
<strong>Explanation:</strong> Return true because &quot;leetcode&quot; can be segmented as &quot;leet code&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;applepenapple&quot;, wordDict = [&quot;apple&quot;,&quot;pen&quot;]
<strong>Output:</strong> true
<strong>Explanation:</strong> Return true because &quot;applepenapple&quot; can be segmented as &quot;apple pen apple&quot;.
Note that you are allowed to reuse a dictionary word.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;catsandog&quot;, wordDict = [&quot;cats&quot;,&quot;dog&quot;,&quot;sand&quot;,&quot;and&quot;,&quot;cat&quot;]
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 300</code></li>
	<li><code>1 &lt;= wordDict.length &lt;= 1000</code></li>
	<li><code>1 &lt;= wordDict[i].length &lt;= 20</code></li>
	<li><code>s</code> and <code>wordDict[i]</code> consist of only lowercase English letters.</li>
	<li>All the strings of <code>wordDict</code> are <strong>unique</strong>.</li>
</ul>

class Solution {
public:
    bool OPT(const unordered_set<string>& dict, vector<vector<int>>& memo, const string& s, int start, int length){
        if (start + length > s.size())
            return false;
        else if (start + length == s.size() && dict.count(s.substr(start, length))){
            return true;
        }
        
        if (memo[start][length - 1] != -1){
            return memo[start][length - 1];
        }

        string substr = s.substr(start, length);
        if (dict.count(substr)){
            memo[start][length - 1] = max(OPT(dict, memo, s, start + length, 1), OPT(dict, memo, s, start, length + 1));
        }
        else{
            memo[start][length - 1] = OPT(dict, memo, s, start, length + 1);
        }

        return memo[start][length - 1];
    }
    bool wordBreak(string s, vector<string>& wordDict) {
        unordered_set<string> dict;
        vector<vector<int>> memo(s.size(), vector<int>(s.size(), - 1));

        for (auto& word : wordDict){
            dict.emplace(word);
        }

        return OPT(dict, memo, s, 0, 1);
    }
};
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