<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:
    int lengthOfLongestSubstring(string s) {
        vector<int> length(s.length());
        deque<char> subString(0);

        if (s.empty()) return 0;
        length[0] = 1;
        subString.push_back(s[0]);
        
        for (int i=1; i<s.length(); i++) {
            if (inQueue(subString, s[i]) == -1) {
                length[i] = length[i-1] + 1;
                subString.push_back(s[i]);
            }
            else {
                int index = inQueue(subString, s[i]);

                for (int i=0; i<index + 1; i++)
                    subString.pop_front();
                subString.push_back(s[i]);

                length[i] = length[i-1] - index;
            }
        }

        return maxInVec(length);
    }

    

private:

    // return the index of target in q if exists, return -1 if not exists
    int inQueue(deque<char> q, char target) {
        for (int i=0; i<q.size(); i++) {
            if (q[i] == target) return i;
        }
        return -1;
    }

    int maxInVec(vector<int> v) {
        int max = 0;
        for (auto it=v.begin(); it<v.end(); it++) {
            if (*it > max) max = *it;
        }
        return max;
    }
};
114055