Longest Contiguous Stretch of Distinct Characters in a String

Given a string s, return the length of the longest substring of s in which every character differs from every other character.

A substring is a contiguous block of characters of s. The empty string counts as a substring, so an empty input has answer 0. Characters are compared exactly as given: an uppercase letter and its lowercase form are different characters, and spaces, digits and punctuation are ordinary characters that can repeat like any other.

Function Signature

def longest_distinct_substring_length(s: str) -> int:

Rules

• Only contiguous substrings count. Picking characters that are not adjacent in s does not form a substring.
• Return only the length. Several different substrings may share the maximum length; the length is still a single, unique answer.

Constraints

• 0 <= len(s) <= 50000
• Every character of s is printable ASCII (character codes 32 through 126): letters, digits, symbols and the space character.
• Because there are only 95 such characters, the answer is between 0 and min(len(s), 95).

Examples

Example 1

Input: s = "streets"
Output: 4

The substring "stre" has four distinct characters. Making it one character longer would include a second "e", and no substring of five or more characters is free of repeats.

Example 2

Input: s = "aAbBa"
Output: 4

"aAbB" and "AbBa" both have four distinct characters, because "a" and "A" are different. The whole string repeats "a".

Example 3

Input: s = ""
Output: 0

The only substring of the empty string is the empty string itself.