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
const DIGITS: &'static str = "零一二三四五六七八九";
const TENS_NAME: &'static str = "个十百千";
const UNIT_RANK: &'static str = "个十百千万亿";
fn digit_pos_to_name(pos: usize) -> char {
if pos == 0 {
'个'
} else if pos % 8 == 0 {
'亿'
} else if pos % 4 == 0 {
'万'
} else {
TENS_NAME.chars().nth(pos % 4).unwrap()
}
}
struct ResultS (String, bool, char);
fn append_digit(result: ResultS, tuple: (usize, char)) -> ResultS {
let (digit, this_unit) = tuple;
let ResultS(mut result, pending_zero, last_unit) = result;
let this_str = DIGITS.chars().nth(digit).unwrap();
if digit == 0 {
if UNIT_RANK.find(last_unit).unwrap() > UNIT_RANK.find(this_unit).unwrap() {
ResultS(result, true, last_unit)
} else {
result.push(this_unit);
ResultS(result, false, this_unit)
}
} else {
if pending_zero {
result.push('零');
}
result.push(this_str);
result.push(this_unit);
ResultS(result, false, this_unit)
}
}
pub fn to_chinese_num(n: &str) -> Option<String> {
if n == "0" {
return Some("零".to_owned());
}
if !n.chars().all(|x| x.is_digit(10)) || n.len() == 0
|| n.chars().nth(0).unwrap() == '0' {
return None;
}
let v = n.as_bytes().iter().rev().enumerate().map(
|(i, c)| ((c - '0' as u8) as usize, digit_pos_to_name(i)))
.rev().fold(ResultS(String::new(), false, '个'), append_digit);
let mut r = v.0;
if r.chars().last().unwrap() == '个' {
r.pop();;
}
if r.starts_with("一十") {
r.remove(0);
}
Some(r)
}
#[test]
fn empty_number() {
let s = to_chinese_num("");
assert!(s.is_none());
}
#[test]
fn num_0() {
let s = to_chinese_num("0").unwrap();
assert_eq!(s, "零");
}
#[test]
fn num_1() {
let s = to_chinese_num("1").unwrap();
assert_eq!(s, "一");
}
#[test]
fn num_10() {
let s = to_chinese_num("10").unwrap();
assert_eq!(s, "十");
}
#[test]
fn num_12() {
let s = to_chinese_num("12").unwrap();
assert_eq!(s, "十二");
}
#[test]
fn num_20() {
let s = to_chinese_num("20").unwrap();
assert_eq!(s, "二十");
}