SET $19$

Given a string, find the length of the longest substring that contains no repeating characters.

Example $1$:

Input: "ABCDEFGABEF"

Explanation: The longest substring without repeating characters are $"$ ABCDEFG $",$

Output: $7$

"BCDEFGA", and "CDEFGAB" with lengths of $7$

Example $2$:

Input: "ABCABCBB"

Output: $3$

Example $3$:

Input: "FIFTYFIVE"

Output: $6$

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