<p>Given a string <code>s</code>, find the length of the <strong>longest</strong> <span data-keyword="substring-nonempty"><strong>substring</strong></span> without repeating characters.</p>

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

<pre>
<strong>Input:</strong> s = &quot;abcabcbb&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong> The answer is &quot;abc&quot;, with the length of 3.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;bbbbb&quot;
<strong>Output:</strong> 1
<strong>Explanation:</strong> The answer is &quot;b&quot;, with the length of 1.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;pwwkew&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong> The answer is &quot;wke&quot;, with the length of 3.
Notice that the answer must be a substring, &quot;pwke&quot; is a subsequence and not a substring.
</pre>

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

<ul>
	<li><code>0 &lt;= s.length &lt;= 5 * 10<sup>4</sup></code></li>
	<li><code>s</code> consists of English letters, digits, symbols and spaces.</li>
</ul>

class Solution {
public:
    bool checkRepeat(const std::queue<char>& vec, char s) {
        std::queue<char> temp = vec;
        while (!temp.empty()) {
            if (temp.front() == s) return false;
            temp.pop();
        }
        return true;
    }

    int lengthOfLongestSubstring(const std::string& s) {
        size_t count = 0;
        std::queue<char> vec;

        if (s.empty()) return 0;

        vec.push(s[0]);

        for (size_t i = 1; i < s.size(); i++) {
            if (checkRepeat(vec, s[i])) {
                vec.push(s[i]);
            } else {
                count = std::max(count, vec.size());
                while (!vec.empty() && vec.front() != s[i]) {
                    vec.pop();
                }
                if (!vec.empty()) vec.pop();
                vec.push(s[i]);
            }
        }

        return std::max(count, vec.size());
    }
};

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