1
use std::collections::HashSet;
2

3
impl Solution {
4
  pub fn max_unique_split(s: String) -> i32 {
5
    let mut combos = HashSet::new();
6
    let mut max = 0;
7
    let chars: Vec<String> = s.chars().map(|c| c.to_string()).collect();
8
    Self::helper(&mut combos, &chars, &mut max);
9

10
    max as i32
11
  }
12

13
  fn helper(combos: &mut HashSet<String>, chars: &[String], max: &mut usize) {
14
    if !chars.is_empty() {
15
      for i in 0..chars.len() {
16
        let mut substr = chars[0..i + 1]
17
          .iter()
18
          .fold(String::with_capacity(i), |mut new_str, s| {
19
            new_str.push_str(s);
20
            new_str
21
          });
22
        if !combos.contains(&substr) {
23
          combos.insert(substr.clone());
24
          Self::helper(combos, &chars[i + 1..], max);
25
          combos.remove(&substr);
26
        }
27
      }
28
    } else {
29
      if combos.len() > *max {
30
        *max = combos.len();
31
      }
32
    }
33
  }
34
}