<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:
#include <unordered_map>

struct Window {
Window(char initial) {
    table[initial] = 0;
}

void udpate(char c) {
    auto it = table.find(c);
    int index = end++;
    if(it == table.end()) {
        table[c] = index;
    }
    else {
        begin = it->second + 1;
        table[c] = index;
        std::unordered_map<char, int> updated;
        for(auto [c, pos] : table) {
            if(pos >= begin) {
                updated[c] = pos;
            }
        }
        table = std::move(updated);        
    }
}

int len() const {return end-begin;}

private:
std::unordered_map<char, int> table;
int begin = 0;
int end = 1;
};

int lengthOfLongestSubstring(string s) {
    if(s.empty()) {
        return 0;
    }
    Window wndw{s.front()};
    int res = 1;
    std::for_each(s.begin()+1, s.end(), [&wndw, &res](char s){
        wndw.udpate(s);
        res = std::max<int>(res, wndw.len());
    });
    return res;
}
};
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