Longest Run That Shuffles Into a Palindrome

Hard

You get a string digits made of digits. Find the longest non-empty run of consecutive characters whose digits can be rearranged into a palindrome, a string that reads the same forwards and backwards. Return the length of that run.

Example 1

digits="4747123" → 5

The run "47471" can be rearranged into the palindrome "47174": there are two 4s, two 7s and a single 1 that goes in the middle. Nothing longer works: "474712" already has two digits with an odd count.

Example 2

digits="908" → 1

All the digits differ, so only a single-digit run works.

Example 3

digits="1221" → 4

The whole string is already a palindrome.

Constraints

1 ≤ len(digits) ≤ 10⁵
digits contains only the digits 0–9

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Topics

Bit Manipulation Hash Table String

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Input

digits="4747123"

Expected

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