Return the length of the longest substring of s in which no character appears twice. A substring is a run of neighbouring characters, so you cannot skip characters inside it.
Example 1
Input
s = "abbcdab"
Output
4
Explanation
"bcda" and "cdab" both have four different characters. No run of five is free of repeats.
Example 2
Input
s = "aaaa"
Output
1
Explanation
every character is the same, so the longest run without a repeat is a single character.
Example 3
Input
s = ""
Output
0
Explanation
an empty string has no characters at all.
Constraints:
0 <= s.length <= 10^5
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