<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) {
        std::unordered_map<char, int> dict;
        int ans = 0;
        for (int i = 0; i < s.length(); ++i)
        {
            std::unordered_map<char,int>::iterator I = dict.find(s[i]);
            if(I == dict.end())        
                dict[s[i]] = i;        
            else
            {
                if (dict.size() > ans)
                    ans = dict.size();
                std::unordered_map<char, int> temp = dict;
                for (auto& it : temp)            
                    if (it.second < dict[s[i]])
                        dict.erase(it.first);            
                dict[s[i]] = i;
            }
        }
   
        if (dict.size() > ans)
            ans = dict.size();
                return ans;
    }
};
180028