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#3442
Easy Algorithms

Maximum difference between even and odd frequency i

Hash Table String Counting
60.7% acceptance
Feb 25, 2026
394
71
You are given a string s consisting of lowercase English letters. Your task is to find the maximum difference diff = freq(a1) - freq(a2) between the frequency of characters a1 and a2 in the string such that: a1 has an odd frequency in the string. a2 has an even frequency in the string. Return this maximum difference.

Solution

Rust
Time O(n)
Space O(1)
LeetCode
solution.rs 
impl Solution {
  pub fn max_difference(s: String) -> i32 {
    let mut freq = [0i32; 26];
    for b in s.bytes() { freq[(b - b'a') as usize] += 1; }
    let max_odd = freq.iter().filter(|&&f| f > 0 && f % 2 == 1).cloned().max().unwrap_or(0);
    let min_even = freq.iter().filter(|&&f| f > 0 && f % 2 == 0).cloned().min().unwrap_or(0);
    max_odd - min_even
  }
}