Longest Repeating Character Replacement LeetCode solution in Rust

1
use std::cmp::max;
2
const NUM_ALPHA: usize = 26;
3

4
impl Solution {
5
  pub fn character_replacement(s: String, k: i32) -> i32 {
6
    let mut counts: [usize; NUM_ALPHA] = [0; NUM_ALPHA];
7
    let s = s.chars().collect::<Vec<_>>();
8
    (0..s.len())
9
      .fold((0, 0, 0), |(res_len, mut maxf, mut l), r| {
10
        counts[(s[r] as u8 - b'A') as usize] += 1;
11
        maxf = max(maxf, counts[(s[r] as u8 - b'A') as usize]);
12
        if (r - l + 1) - maxf > k as usize {
13
          counts[(s[l] as u8 - b'A') as usize] -= 1;
14
          l += 1;
15
        }
16
        (max(res_len, r - l + 1), maxf, l)
17
      })
18
      .0 as i32
19
  }
20
}