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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
pub fn pad(size: usize, input: &[bool]) -> Vec<bool> {
let input_len = input.len();
let mut out: Vec<bool> = Vec::new();
for _ in input_len..size {
out.push(false);
}
for item in input.iter() {
out.push(item.clone());
}
out
}
fn find_seq(initial: bool, collection: &[bool]) -> usize {
let mut final_count = 0;
let mut expected_value = initial;
for entry in collection {
if *entry == expected_value {
final_count += 1;
} else {
break;
}
if expected_value == initial {
expected_value = !initial;
}
}
final_count
}
pub fn shared_prefix<'a>(start: &'a [bool], end: &[bool]) -> &'a [bool] {
let pairs = start.iter().zip(end);
let mut slice_end = 0;
for pair in pairs {
if pair.0 == pair.1 {
slice_end += 1;
} else {
break;
}
}
&start[0..slice_end]
}
pub fn range_prefix<'a, 'b>(start: &'a [bool], end: &'b [bool]) -> (&'a [bool], &'b [bool]) {
let segment_len = end.len();
let base = shared_prefix(&start, end);
let base_len = base.len();
let start_special = find_seq(false, &start[base_len..segment_len]);
let end_special = find_seq(true, &end[base_len..segment_len]);
let start_prefix_len = base_len + start_special;
let end_prefix_len = base_len + end_special;
(&start[0..start_prefix_len], &end[0..end_prefix_len])
}
#[cfg(test)]
mod tests {
use std::fmt::Debug;
use std::cmp::PartialEq;
use super::*;
fn assert_vec_equal<T>(a: &[T], b: &[T]) where T: Debug, T: PartialEq {
let pairs = a.iter().zip(b);
for entry in pairs {
assert_eq!(entry.0, entry.1);
}
}
#[test]
fn finds_shared_prefix() {
let start = vec![true, false, true, false, true, false, false, false, true, true];
let end = vec![true, false, true, false, true, false, false, true, true, true];
let expected = &start[0..7];
let result = shared_prefix(&start, &end);
assert_vec_equal(result, expected);
}
#[test]
fn gets_agressive_prefix() {
let start = vec![true, false, true, false, true, false, false, false, true, true];
let end = vec![true, false, true, false, true, false, false, true, true, true];
let start_prefix = vec![true, false, true, false, true, false, false, false, true, true];
let end_prefix = vec![true, false, true, false, true, false, false, true];
let result = range_prefix(&start, &end);
assert_vec_equal(&start_prefix, result.0);
assert_vec_equal(&end_prefix, result.1);
}
#[test]
fn do_pad_vec() {
let expected = [false, true, false];
let result = pad(3, &vec![true, false]);
assert_vec_equal(&result, &expected);
}
#[test]
fn pad_empty() {
let expected = [false, false, false];
let input: Vec<bool> = Vec::new();
let result = pad(3, &input);
assert_vec_equal(&result, &expected);
}
#[test]
fn no_pad() {
let expected = [false, true, false];
let result = pad(3, &vec![false, true, false]);
assert_vec_equal(&result, &expected);
}
}