<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>

/*
given a dictionary decide if a word can be made from the words in the dict (mutlip usage allowed)

This is a search space traversal problem where we have words to concat together to make a target work

dfs with back tracking while trying out the words of the dictionary. 

*/

class Solution {
public:
    bool wordBreak(string s, vector<string>& wordDict) {
        string path = "";
        unordered_set<string> visited{};
        return dfs(s, path, wordDict, visited);
    }

    bool dfs(string s, string& path, vector<string>& wordDict, unordered_set<string>& visited){
        if (path.size() > 0 && s == path){
            return true;    
        }
        if (path.size() > 0 && !s.starts_with(path)){
            return false;
        }
        bool result = false;
        for (const string& word : wordDict){
            string newPath = path+ word;
            if (newPath.size() > s.size() || visited.count(newPath) != 0){
                continue;
            }
            result = result || dfs(s, newPath, wordDict, visited);
            visited.emplace(newPath);
            if (result){
                return true;
            }
        }

        return result;
    }
};
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