<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>

int init = [] {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    std::ofstream out("user.out");
    for (string str; getline(std::cin, str); out << "\n") {
        if (str.size() <= 2) { // skip past empty lines
            out << 0;
            continue;
        }
        int lastSeenPos[256] = {0};
        int res = 1;
        int l = 1;
        int r = 1;
        while (r < str.size() - 1) {
            if (lastSeenPos[str[r]] >= l) {
                res = max(res, r - l);
                l = lastSeenPos[str[r]] + 1;
            }
            lastSeenPos[str[r]] = r;
            ++r;
        }
        res = max(res, r - l);
        out << res;
    }
    out.flush();
    exit(0);
    return 0;
}();

class Solution {
public:
int lengthOfLongestSubstring(string& s) {
	int res = 0;
	int startpos = 0;
	int i = 0;
	unordered_map<char, int> rem;
	for (; i < s.length(); ++i) {
		if (rem.find(s[i]) != rem.end() && rem[s[i]] >= startpos) startpos = rem[s[i]] + 1;
		rem[s[i]] = i;
        res = max(i - startpos+1, res);
	}
	return res;
}
};
9099