fenwick-tree 0.1.0

An implementation of a binary indexed tree (Fenwick tree) data structure in Rust.
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
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use std::ops::Bound;

use crate::*;

#[test]
fn sum_of_empty_range_is_0() {
    let tree = new_tree(3);

    assert_eq!(tree.sum(0..0).unwrap(), 0);
}

#[test]
fn sum_of_decreasing_range_is_0() {
    let tree = new_tree(3);

    assert_eq!(tree.sum(2..0).unwrap(), 0);
}

#[test]
fn sum_of_range_with_too_big_lower_bound_is_err() {
    let tree = new_tree(3);

    let err = tree.sum(3..4).expect_err("");

    assert_eq!(
        SumError::OutOfRange {
            bounds: (Bound::Included(3), Bound::Excluded(4)),
            len: 3
        },
        err
    );
}

#[test]
fn sum_of_range_with_too_big_upper_bound_is_err() {
    let tree = new_tree(3);

    let err = tree.sum(0..=4).expect_err("");

    assert_eq!(
        SumError::OutOfRange {
            bounds: (Bound::Included(0), Bound::Included(4)),
            len: 3
        },
        err
    );
}

#[test]
fn adding_at_invalid_index_is_err() {
    let mut tree = new_tree(3);

    let err = tree.add(4, 0).expect_err("");

    assert_eq!(AddError::IndexOutOfRange { index: 4, size: 3 }, err);
}

#[test]
fn range_sum_is_calculated_correctly_for_range() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(0..3).unwrap(), 1 + 2 + 3);
}

#[test]
fn range_sum_is_calculated_correctly_for_range_from() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(0..).unwrap(), 1 + 2 + 3);
    assert_eq!(tree.sum(1..).unwrap(), 2 + 3);
}

#[test]
fn range_sum_is_calculated_correctly_for_range_to() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(..3).unwrap(), 1 + 2 + 3);
    assert_eq!(tree.sum(..2).unwrap(), 1 + 2);
}

#[test]
fn range_sum_is_calculated_correctly_for_range_full() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(..).unwrap(), 1 + 2 + 3);
}

#[test]
fn range_sum_is_calculated_correctly_for_range_inclusive() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(0..=2).unwrap(), 1 + 2 + 3);
    assert_eq!(tree.sum(0..=1).unwrap(), 1 + 2);
}

#[test]
fn range_sum_is_calculated_correctly_for_range_to_inclusive() {
    let tree = new_filled_tree(3);

    assert_eq!(tree.sum(..=2).unwrap(), 1 + 2 + 3);
    assert_eq!(tree.sum(..=1).unwrap(), 1 + 2);
}

#[test]
fn range_sum_is_calculated_correctly_for_custom_bounds() {
    let tree = new_filled_tree(3);

    assert_eq!(
        tree.sum((Bound::Included(0), Bound::Excluded(1))).unwrap(),
        1
    );

    assert_eq!(
        tree.sum((Bound::Excluded(0), Bound::Included(1))).unwrap(),
        2
    );
}

fn new_filled_tree(size: usize) -> FenwickTree<i32> {
    let mut tree = new_tree(size);

    for i in 1..=size {
        tree.add(i - 1, i as i32).unwrap();
    }

    tree
}

fn new_tree(size: usize) -> FenwickTree<i32> {
    FenwickTree::<i32>::with_len(size)
}