rustgym 0.2.0

rustgym solutions
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63

#[derive(Default)]
struct CombinationIterator {
    combinations: Vec<String>,
    index: usize,
}

impl CombinationIterator {
    fn new(characters: String, combination_length: i32) -> Self {
        let n = combination_length as usize;
        let m = characters.len();
        let mut indexes = vec![];
        let mut combinations = vec![];
        let s: Vec<char> = characters.chars().collect();
        Self::dfs(0, &mut indexes, &mut combinations, &s, n, m);
        let index = 0;
        CombinationIterator {
            combinations,
            index,
        }
    }

    fn dfs(
        start: usize,
        indexes: &mut Vec<usize>,
        combinations: &mut Vec<String>,
        s: &[char],
        n: usize,
        m: usize,
    ) {
        if indexes.len() == n {
            let t: String = indexes.iter().map(|&i| s[i]).collect();
            combinations.push(t);
        } else {
            for i in start..m {
                indexes.push(i);
                Self::dfs(i + 1, indexes, combinations, s, n, m);
                indexes.pop();
            }
        }
    }

    fn next(&mut self) -> String {
        let res = self.combinations[self.index].to_string();
        self.index += 1;
        res
    }

    fn has_next(&self) -> bool {
        self.index < self.combinations.len()
    }
}

#[test]
fn test() {
    let mut iter = CombinationIterator::new("abc".to_string(), 2);
    assert_eq!(iter.has_next(), true);
    assert_eq!(iter.next(), "ab".to_string());
    assert_eq!(iter.has_next(), true);
    assert_eq!(iter.next(), "ac".to_string());
    assert_eq!(iter.has_next(), true);
    assert_eq!(iter.next(), "bc".to_string());
    assert_eq!(iter.has_next(), false);
}