<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 find(string s, int sz)
    {
        vector<int> check(256, 0);
        int cnt = 0;
        int i=0;
        for(; i<sz; i++)
        {
            if(check[s[i]-' ']==0)
            {
                cnt++;
            }
            check[s[i]-' ']++;
        }
        if(cnt==sz)
        return true;
        while(i<s.size())
        {
            check[s[i-sz]-' ']--;
            if(check[s[i-sz]-' ']==0)
            cnt--;
            if(check[s[i]-' ']==0)
            {
                cnt++;
            }
            check[s[i]-' ']++; 
            if(cnt==sz)
            return true;
            i++;
        }
        return false;

    }
    int lengthOfLongestSubstring(string s) {
        int low=1, high=256;

        while(low<=high)
        {
            int mid = (low+high)/2;
            if(mid>s.size())
            {
                high = mid - 1;
            }
            else if(find(s, mid))
            low = mid + 1;
            else high = mid - 1;
        }
        return high;
    }
};
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