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
| use std::{collections::HashMap};
type MonkeyId = u32;
static ROOT_ID: MonkeyId = 0x746F6F72;
static HUMN_ID: MonkeyId = 0x6E6D7568;
#[derive(Debug, PartialEq, Clone, Copy)]
pub enum Op {
Add,
Sub,
Mul,
Div,
}
impl Op {
fn perform_op(&self, a: i64, b: i64) -> i64 {
match self {
Op::Add => a + b,
Op::Sub => a - b,
Op::Mul => a * b,
Op::Div => a / b,
}
}
}
#[derive(Debug, PartialEq, Clone)]
pub enum Monkey {
Yell(i64),
Parent(Box<(Monkey, Op, Monkey)>),
Human(i64),
}
impl Monkey {
fn from_str(id: MonkeyId, known_values: &HashMap<MonkeyId, String>) -> Self {
let s = known_values.get(&id).unwrap();
if s.chars().filter(|c| c.is_numeric()).count() > 0 {
let n = s.parse::<i64>().unwrap();
if id == HUMN_ID {
Monkey::Human(n)
} else {
Monkey::Yell(n)
}
} else {
let mut args = s.splitn(3, ' ');
let lhs = Monkey::from_str(str_id_to_monkey_id(args.next().unwrap()), known_values);
let op = match args.next().unwrap() {
"+" => Op::Add,
"-" => Op::Sub,
"*" => Op::Mul,
"/" => Op::Div,
_ => panic!("\"{}\" is not a valid math operator", args.next().unwrap()),
};
let rhs = Monkey::from_str(str_id_to_monkey_id(args.next().unwrap()), known_values);
Monkey::Parent(Box::new((lhs, op, rhs)))
}
}
fn into_children(self) -> (Monkey, Op, Monkey) {
if let Monkey::Parent(b) = self {
*b
} else {
panic!("attempted to get children of a non-parent")
}
}
fn value(&self) -> i64 {
match self {
Monkey::Yell(n) | Monkey::Human(n) => *n,
Monkey::Parent(b) => {
let (lhs, op, rhs) = b.as_ref();
op.perform_op(lhs.value(), rhs.value())
}
}
}
fn make_constant(&mut self) {
if let Monkey::Parent(b) = self {
let (lhs, op, rhs) = b.as_mut();
lhs.make_constant();
rhs.make_constant();
if let (Monkey::Yell(a), Monkey::Yell(b)) = (lhs, rhs) {
*self = Monkey::Yell(op.perform_op(*a, *b));
}
}
}
fn undo_op(self, h: &mut i64) -> Monkey {
let (lhs, op, rhs) = self.into_children();
match op {
Op::Add => {
let (cons, var) = if matches!(lhs, Monkey::Yell(..)) {
(lhs, rhs)
} else {
(rhs, lhs)
};
*h -= cons.value();
var
}
Op::Sub => {
if let Monkey::Yell(n) = lhs {
*h = n - *h;
rhs
} else if let Monkey::Yell(n) = rhs {
*h += n;
lhs
} else {
unreachable!()
}
}
Op::Mul => {
let (cons, var) = if matches!(lhs, Monkey::Yell(..)) {
(lhs, rhs)
} else {
(rhs, lhs)
};
*h /= cons.value();
var
}
Op::Div => {
if let Monkey::Yell(n) = lhs {
*h = n / *h;
rhs
} else if let Monkey::Yell(n) = rhs {
*h *= n;
lhs
} else {
unreachable!()
}
}
}
}
fn solve_for_humn(mut self) -> i64 {
self.make_constant();
let (lhs, _, rhs) = self.into_children();
let (constant_side, mut human_side) = if matches!(lhs, Monkey::Yell(..)) {
(lhs, rhs)
} else {
(rhs, lhs)
};
let mut h = constant_side.value();
while !matches!(human_side, Monkey::Human(..)) {
human_side = human_side.undo_op(&mut h);
}
h
}
}
type Input = Monkey;
fn parse(input: &str) -> Input {
let known_values = input.lines().filter_map(|line| {
let (id, yell_str) = line.split_once(": ")?;
Some((str_id_to_monkey_id(id), yell_str.to_string()))
}).collect();
Monkey::from_str(ROOT_ID, &known_values)
}
fn str_id_to_monkey_id(id: &str) -> MonkeyId {
let id = id.as_bytes();
u32::from_le_bytes([id[0], id[1], id[2], id[3]])
}
pub fn part_one(input: Input) -> Option<i64> {
Some(input.value())
}
pub fn part_two(input: Input) -> Option<i64> {
Some(input.solve_for_humn())
}
|