Maximum length substring with two occurrences

Hash Table String Sliding Window

65.2% acceptance

Feb 25, 2026

253

Given a string s, return the maximum length of a substring such that it contains at most two occurrences of each character.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn maximum_length_substring(s: String) -> i32 {
    let b = s.as_bytes();
    let n = b.len();
    let mut freq = [0u8; 26];
    let mut l = 0;
    let mut ans = 0;
    for r in 0..n {
      freq[(b[r] - b'a') as usize] += 1;
      while freq[(b[r] - b'a') as usize] > 2 {
        freq[(b[l] - b'a') as usize] -= 1;
        l += 1;
      }
      ans = ans.max(r - l + 1);
    }
    ans as i32
  }
}