dsalgo 0.3.10

A package for Datastructures and Algorithms.
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
64
65
66
67
68
69

//! interface is 0-indexed.

pub struct Fenwick(Vec<i64>);

impl Fenwick {
    pub fn new(size: usize) -> Self {
        Self(vec![0; size + 1])
    }

    pub fn size(&self) -> usize {
        self.0.len() - 1
    }

    /// add x to a_j (j >= i)

    pub fn add_ge(
        &mut self,
        mut i: usize,
        x: i64,
    ) {
        assert!(i < self.size());

        i += 1;

        while i <= self.size() {
            self.0[i] += x;

            i += 1 << i.trailing_zeros();
        }
    }

    /// get a_i

    pub fn get(
        &self,
        mut i: usize,
    ) -> i64 {
        assert!(i < self.size());

        i += 1;

        let mut v = 0;

        while i > 0 {
            v += self.0[i];

            i -= 1 << i.trailing_zeros();
        }

        v
    }
}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test() {
        let mut fw = Fenwick::new(10);

        fw.add_ge(5, 1); // add 1 for a_j (j >= i);
        assert_eq!(fw.get(4), 0); // get a_4
        assert_eq!(fw.get(5), 1);
    }
}