summary refs log tree commit diff homepage
path: root/2016/src/bin/day23.rs
blob: 4a54983490afd39105ac7159b9c1a1b11a633890 (plain) (blame)
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
use std::io::{self, Read};

#[derive(Clone, Copy)]
enum Operand {
    Register(u8),
    Immediate(i32),
}

impl<'a> From<&'a str> for Operand {
    fn from(s: &'a str) -> Self {
        match s {
            "a" => Operand::Register(0),
            "b" => Operand::Register(1),
            "c" => Operand::Register(2),
            "d" => Operand::Register(3),
            _ => Operand::Immediate(s.parse().unwrap()),
        }
    }
}

#[derive(Clone, Copy)]
enum Operation {
    Cpy(Operand, Operand),
    Inc(Operand),
    Dec(Operand),
    Jnz(Operand, Operand),
    Tgl(Operand),
}

impl<'a> From<&'a str> for Operation {
    fn from(s: &'a str) -> Self {
        let mut iter = s.split_whitespace();
        match (iter.next().unwrap(), iter.next().unwrap()) {
            ("cpy", a) => Operation::Cpy(Operand::from(a), Operand::from(iter.next().unwrap())),
            ("inc", a) => Operation::Inc(Operand::from(a)),
            ("dec", a) => Operation::Dec(Operand::from(a)),
            ("jnz", a) => Operation::Jnz(Operand::from(a), Operand::from(iter.next().unwrap())),
            ("tgl", a) => Operation::Tgl(Operand::from(a)),
            _ => panic!("invalid instruction {}", s),
        }
    }
}

impl Operation {
    fn toggle(self) -> Self {
        match self {
            Operation::Inc(a) => Operation::Dec(a),
            Operation::Dec(a) | Operation::Tgl(a) => Operation::Inc(a),
            Operation::Jnz(a, b) => Operation::Cpy(a, b),
            Operation::Cpy(a, b) => Operation::Jnz(a, b),
        }
    }
}

#[derive(Default)]
struct Vm {
    registers: [i32; 4],
    operations: Vec<Operation>,
    index: i32,
}

impl<'a> From<&'a str> for Vm {
    fn from(s: &'a str) -> Self {
        let mut vm = Self::default();
        for line in s.lines() {
            vm.operations.push(Operation::from(line));
        }
        vm
    }
}

impl Vm {
    fn step(&mut self) -> bool {
        match self.operations[self.index as usize] {
            Operation::Cpy(Operand::Immediate(imm), Operand::Register(reg)) => {
                self.registers[reg as usize] = imm;
                self.index += 1;
            },
            Operation::Cpy(Operand::Register(src), Operand::Register(dest)) => {
                self.registers[dest as usize] = self.registers[src as usize];
                self.index += 1;
            },
            Operation::Inc(Operand::Register(reg)) => {
                self.registers[reg as usize] += 1;
                self.index += 1;
            },
            Operation::Dec(Operand::Register(reg)) => {
                self.registers[reg as usize] -= 1;
                self.index += 1;
            },
            Operation::Jnz(Operand::Immediate(cond), Operand::Immediate(jump)) => {
                if cond != 0 {
                    self.index += jump;
                } else {
                    self.index += 1;
                }
            },
            Operation::Jnz(Operand::Register(reg), Operand::Immediate(jump)) => {
                if self.registers[reg as usize] != 0 {
                    self.index += jump;
                } else {
                    self.index += 1;
                }
            },
            Operation::Jnz(Operand::Immediate(cond), Operand::Register(reg)) => {
                if cond != 0 {
                    self.index += self.registers[reg as usize];
                } else {
                    self.index += 1;
                }
            },
            Operation::Tgl(Operand::Register(reg)) => {
                let index = self.index + self.registers[reg as usize];
                if let Some(operation) = self.operations.get_mut(index as usize) {
                    *operation = operation.toggle();
                }
                self.index += 1;
            },
            _ => {
                self.index += 1;
            },
        }

        (self.index as usize) < self.operations.len()
    }
}

fn solve(initial: i32, input: &str) -> i32 {
    let mut vm = Vm::from(input);
    vm.registers[0] = initial;
    while vm.step() { }
    vm.registers[0]
}

fn main() {
    let mut input = String::new();
    io::stdin().read_to_string(&mut input).unwrap();

    println!("Part 1: {}", solve(7, &input));
    println!("Part 2: {}", solve(12, &input));
}

#[test]
fn part1() {
    let input = "
cpy 2 a
tgl a
tgl a
tgl a
cpy 1 a
dec a
dec a
";
    let mut vm = Vm::from(input.trim());
    while vm.step() { }
    assert_eq!(3, vm.registers[0]);
}