Maximum Difference Between Even And Odd Frequency I

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Maximum Difference Between Even And Odd Frequency I

Find the maximum difference between the frequencies of two characters whose counts have opposite parity.

Acceptance 100%

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Problem Statement

Given a string s, count how many times each character appears.

Your task is to find the largest possible value of:

\text{frequency of one character} - \text{frequency of another character}

subject to the following condition:

the first character must have an even frequency,
the second character must have an odd frequency,
the two characters may be different.

If no valid pair of characters exists, return the closest safe answer for the problem variant, which is typically 0.

This is a frequency-analysis problem where you compare character counts and look for the best even-minus-odd difference.

Input Format

A string s consisting of lowercase English letters.
You may assume the string is non-empty unless the platform statement says otherwise.

Output Format

Return an integer: the maximum value of evenFrequency - oddFrequency over all valid character pairs.
If no valid pair exists, return 0.

Constraints

1 <= s.length <= $10^{5}$ is a reasonable interview-style assumption for this variant.
Characters are typically lowercase English letters.
Time should be linear or near-linear in the length of the string.

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