Max Difference You Can Get From Changing an Integer LeetCode solution in Rust

1
impl Solution {
2
  pub fn max_diff(num: i32) -> i32 {
3
    let mut a = vec![];
4
    let mut num = num;
5
    while num > 9 {
6
      a.push(num % 10);
7
      num /= 10;
8
    }
9
    a.push(num);
10
    a.reverse();
11

12
    let mut b = a.clone();
13
    let mut x = -1;
14
    let mut y = (-1, 0);
15
    for i in 0..a.len() {
16
      if x != -1 {
17
        if a[i] == x {
18
          a[i] = 9;
19
        }
20
      } else {
21
        if a[i] != 9 {
22
          x = a[i];
23
          a[i] = 9;
24
        }
25
      }
26
    }
27

28
    if b[0] != 1 {
29
      y.0 = b[0];
30
      y.1 = 1;
31
      b[0] = 1;
32
    }
33
    for i in 1..b.len() {
34
      if y.0 != -1 {
35
        if b[i] == y.0 {
36
          b[i] = y.1;
37
        }
38
      } else {
39
        if b[i] > 1 {
40
          y.0 = b[i];
41
          b[i] = 0;
42
        }
43
      }
44
    }
45
    let mut result = 0;
46
    for i in 0..a.len() - 1 {
47
      result += a[i] - b[i];
48
      result *= 10;
49
    }
50

51
    result + a.last().unwrap() - b.last().unwrap()
52
  }
53
}