diff --git a/day-8/.gitignore b/day-8/.gitignore
new file mode 100644
index 0000000..b83d222
--- /dev/null
+++ b/day-8/.gitignore
@@ -0,0 +1 @@
+/target/
diff --git a/day-8/Cargo.lock b/day-8/Cargo.lock
new file mode 100644
index 0000000..81f3040
--- /dev/null
+++ b/day-8/Cargo.lock
@@ -0,0 +1,106 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "day-8"
+version = "0.1.0"
+dependencies = [
+ "indoc",
+ "snafu",
+]
+
+[[package]]
+name = "doc-comment"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fea41bba32d969b513997752735605054bc0dfa92b4c56bf1189f2e174be7a10"
+
+[[package]]
+name = "indoc"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "47741a8bc60fb26eb8d6e0238bbb26d8575ff623fdc97b1a2c00c050b9684ed8"
+dependencies = [
+ "indoc-impl",
+ "proc-macro-hack",
+]
+
+[[package]]
+name = "indoc-impl"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce046d161f000fffde5f432a0d034d0341dc152643b2598ed5bfce44c4f3a8f0"
+dependencies = [
+ "proc-macro-hack",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "unindent",
+]
+
+[[package]]
+name = "proc-macro-hack"
+version = "0.5.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbf0c48bc1d91375ae5c3cd81e3722dff1abcf81a30960240640d223f59fe0e5"
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e0704ee1a7e00d7bb417d0770ea303c1bccbabf0ef1667dae92b5967f5f8a71"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "snafu"
+version = "0.6.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eab12d3c261b2308b0d80c26fffb58d17eba81a4be97890101f416b478c79ca7"
+dependencies = [
+ "doc-comment",
+ "snafu-derive",
+]
+
+[[package]]
+name = "snafu-derive"
+version = "0.6.10"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1508efa03c362e23817f96cde18abed596a25219a8b2c66e8db33c03543d315b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.54"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a2af957a63d6bd42255c359c93d9bfdb97076bd3b820897ce55ffbfbf107f44"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-xid",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
+
+[[package]]
+name = "unindent"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f14ee04d9415b52b3aeab06258a3f07093182b88ba0f9b8d203f211a7a7d41c7"
diff --git a/day-8/Cargo.toml b/day-8/Cargo.toml
new file mode 100644
index 0000000..9cc66ff
--- /dev/null
+++ b/day-8/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "day-8"
+version = "0.1.0"
+authors = ["Tristan Daniël Maat <tm@tlater.net>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+indoc = "0.3"
+snafu = "0.6"
diff --git a/day-8/input b/day-8/input
new file mode 100644
index 0000000..764999d
--- /dev/null
+++ b/day-8/input
@@ -0,0 +1,612 @@
+jmp +236
+acc +43
+acc +28
+jmp +149
+acc +28
+acc +13
+acc +36
+acc +42
+jmp +439
+acc -14
+jmp +29
+jmp +154
+acc +16
+acc -13
+acc -16
+nop +317
+jmp +497
+acc +21
+jmp +386
+jmp +373
+acc +22
+jmp +311
+acc -16
+acc +27
+acc +21
+acc +43
+jmp +512
+jmp +218
+jmp +217
+acc +12
+acc +44
+nop +367
+nop +180
+jmp +134
+acc -2
+acc +42
+acc +13
+acc -11
+jmp +442
+nop +457
+jmp +151
+acc +15
+acc -4
+acc +0
+jmp +131
+acc +6
+acc -2
+acc +37
+jmp +112
+acc +32
+acc +6
+acc -15
+jmp +474
+jmp +515
+acc +12
+acc +11
+acc +4
+jmp +339
+acc -3
+acc +36
+jmp +220
+nop +91
+acc -12
+jmp +49
+acc -17
+jmp +204
+acc +40
+jmp +535
+acc +37
+acc +8
+nop +147
+nop +174
+jmp +306
+jmp +305
+acc +7
+acc +33
+jmp +305
+acc +22
+acc +17
+acc +24
+jmp +458
+jmp +1
+acc +36
+acc +34
+jmp +113
+acc -3
+nop +113
+nop -34
+jmp +506
+acc -19
+acc +21
+acc +35
+acc -1
+jmp +74
+acc +15
+acc +7
+jmp +79
+acc +29
+acc +42
+jmp +427
+acc +33
+jmp +29
+acc +6
+acc +13
+nop +477
+acc +26
+jmp +493
+acc +33
+acc +43
+acc +49
+acc +35
+jmp +409
+acc -7
+acc +35
+acc +40
+jmp +309
+acc -13
+acc -14
+acc +32
+jmp +322
+jmp +10
+jmp +44
+acc +20
+acc +25
+jmp +175
+acc +22
+acc +16
+acc +1
+acc +36
+jmp -65
+jmp +231
+acc +35
+jmp +155
+jmp +218
+acc -10
+acc -13
+acc +38
+jmp -92
+acc +15
+jmp +134
+acc -16
+acc +18
+jmp -30
+nop -41
+acc +48
+acc +49
+jmp -107
+acc +4
+acc +34
+acc +38
+acc -18
+jmp +247
+acc +45
+acc +23
+jmp +149
+nop +164
+acc +26
+jmp -24
+jmp +240
+jmp +77
+acc +30
+acc -13
+jmp -158
+nop +136
+jmp +33
+jmp +189
+jmp +143
+jmp +1
+acc +4
+acc +30
+jmp -106
+acc +16
+nop -52
+acc +37
+jmp +119
+acc -11
+acc -9
+acc +15
+acc +4
+jmp +301
+jmp +1
+acc -3
+jmp +188
+nop +86
+nop +125
+acc -10
+jmp -105
+acc +36
+acc +9
+acc +0
+jmp +317
+jmp +347
+acc +48
+nop +380
+acc -18
+acc +28
+jmp +398
+jmp -152
+jmp -86
+acc +22
+acc +11
+acc +39
+jmp -173
+jmp +343
+nop +194
+nop +98
+nop +382
+jmp +300
+acc +35
+nop +287
+acc -8
+jmp +302
+acc +19
+acc +45
+jmp +95
+acc +29
+jmp +274
+acc +18
+acc -13
+acc +23
+acc +7
+jmp +164
+acc +17
+acc +36
+acc -5
+jmp +153
+acc +21
+jmp +105
+jmp +1
+nop +267
+jmp +277
+jmp +88
+acc +2
+acc +18
+nop +182
+jmp +189
+acc +37
+acc +46
+jmp +258
+acc +22
+acc +15
+jmp +249
+acc +17
+jmp -162
+jmp +25
+acc -6
+nop +314
+jmp -30
+jmp +312
+acc +34
+nop -230
+acc -2
+jmp +158
+acc -4
+acc +37
+jmp +318
+acc +18
+acc +23
+acc -8
+jmp -248
+jmp +181
+acc +17
+acc +4
+jmp -189
+acc +27
+acc -13
+acc -4
+acc +8
+jmp +222
+jmp +310
+acc -5
+acc +35
+jmp +241
+jmp -130
+jmp +124
+acc -19
+jmp +331
+acc -8
+acc +45
+jmp +106
+acc +23
+acc +48
+jmp -107
+acc +7
+acc -19
+acc +3
+jmp +130
+jmp -104
+nop +5
+acc +29
+acc +8
+acc -6
+jmp +7
+acc +12
+jmp +102
+acc -4
+acc +46
+acc -17
+jmp -209
+acc +20
+jmp -271
+acc +48
+jmp +30
+nop +204
+acc -19
+acc +4
+acc +38
+jmp +17
+jmp +116
+acc -17
+acc +23
+jmp -75
+jmp -129
+jmp +152
+acc +36
+nop -193
+acc +26
+acc +38
+jmp +242
+jmp -197
+acc +32
+acc -5
+acc -19
+jmp -201
+jmp -304
+acc +9
+jmp +175
+acc +1
+jmp -15
+jmp +1
+nop -74
+jmp -38
+nop -165
+acc -19
+jmp -317
+acc -19
+acc -1
+jmp +17
+acc +0
+nop +151
+jmp +93
+acc +32
+acc +29
+acc +0
+jmp -340
+acc +39
+jmp -115
+acc +0
+acc +47
+nop -320
+jmp +244
+acc +29
+jmp +81
+jmp -84
+acc +2
+acc +16
+nop -345
+acc +23
+jmp +9
+acc +26
+jmp -67
+acc -11
+acc +38
+jmp +150
+acc +19
+acc -2
+jmp -244
+jmp +88
+acc -4
+jmp -157
+acc +22
+acc +33
+acc +41
+jmp -117
+acc +31
+acc +50
+acc +24
+jmp -265
+jmp +1
+jmp -352
+jmp -312
+acc +35
+acc +30
+jmp -90
+jmp +8
+acc +14
+acc +39
+jmp -112
+acc -11
+acc -3
+acc +22
+jmp -116
+acc +48
+jmp -194
+acc -5
+jmp -252
+jmp +66
+jmp -295
+jmp +196
+acc +25
+acc -11
+nop +112
+acc +33
+jmp +123
+acc -10
+acc +28
+nop -119
+acc +12
+jmp -166
+jmp -356
+acc +8
+acc +16
+jmp +161
+acc +25
+acc +3
+jmp -5
+acc +32
+acc +40
+jmp +181
+acc -11
+acc -5
+jmp +1
+acc +0
+jmp -265
+acc +5
+acc +24
+acc +15
+acc -17
+jmp -326
+nop +103
+acc -9
+acc +13
+jmp -379
+acc +38
+acc +16
+jmp -65
+jmp +1
+jmp +1
+jmp +1
+acc -1
+jmp -191
+acc +35
+acc -19
+acc -6
+jmp -52
+acc +15
+jmp -357
+nop -134
+acc -3
+nop +103
+jmp -123
+acc +43
+acc +0
+acc +47
+jmp -373
+acc +0
+acc +50
+acc +44
+acc +21
+jmp -114
+acc -19
+jmp -339
+acc +25
+jmp -410
+jmp -126
+acc -2
+acc -6
+acc +14
+jmp -207
+acc +35
+acc -7
+jmp +75
+acc +9
+acc +22
+jmp +114
+acc +18
+acc +36
+acc +0
+acc +40
+jmp -192
+acc +35
+acc +0
+acc +28
+acc +3
+jmp -346
+nop -131
+acc +46
+nop -467
+nop -179
+jmp -151
+jmp -120
+acc +30
+acc +22
+acc -7
+acc +18
+jmp -157
+acc +5
+jmp +76
+nop -315
+acc +25
+jmp -357
+acc +44
+jmp -12
+acc +0
+acc +19
+nop -485
+jmp -495
+nop -115
+acc +12
+jmp -8
+acc +31
+acc -7
+jmp -158
+acc +44
+acc +32
+jmp +87
+acc +1
+acc +37
+acc +44
+jmp -86
+acc +0
+acc +17
+acc -13
+jmp -434
+acc +37
+jmp -342
+acc +3
+jmp +1
+acc +29
+jmp -242
+acc +48
+jmp -442
+jmp -283
+acc -19
+acc +6
+acc +20
+acc +44
+jmp -533
+acc -15
+nop -356
+acc +18
+jmp -408
+acc -9
+acc +17
+acc +16
+jmp -385
+nop -130
+jmp +1
+acc +38
+acc +39
+jmp -324
+jmp -141
+acc +4
+acc +3
+acc -4
+jmp -114
+acc +2
+jmp +1
+acc +44
+jmp -360
+acc +43
+acc +36
+nop -177
+nop -288
+jmp -496
+acc +45
+acc +0
+jmp -322
+acc +13
+jmp -511
+acc -2
+acc +36
+jmp -460
+acc +28
+acc +28
+jmp -455
+acc -4
+acc +38
+jmp -145
+jmp -163
+jmp -331
+nop -227
+jmp -470
+acc +35
+nop -419
+acc +39
+acc +0
+jmp -435
+jmp +1
+jmp -69
+acc +20
+acc +46
+nop +2
+jmp -239
+acc -3
+acc +12
+acc +38
+jmp -259
+jmp -60
+jmp -67
+nop -542
+jmp -397
+acc +32
+jmp -57
+acc +30
+nop -393
+jmp -380
+acc +16
+acc -7
+acc +0
+acc +2
+jmp +1
diff --git a/day-8/src/emulator.rs b/day-8/src/emulator.rs
new file mode 100644
index 0000000..c148197
--- /dev/null
+++ b/day-8/src/emulator.rs
@@ -0,0 +1,187 @@
+use std::collections::HashSet;
+
+use snafu::Snafu;
+
+pub type Program = Vec<(Instruction, i64)>;
+
+#[derive(Debug, PartialEq, Snafu)]
+pub enum EmulatorError {
+ #[snafu(display("Segmentation fault"))]
+ SegmentationFault,
+ #[snafu(display("Infinite loop: {}", accumulator))]
+ InfiniteLoop { accumulator: i64 },
+}
+
+#[derive(Debug, Snafu)]
+pub enum ProgramParseError {
+ #[snafu(display("Invalid instruction given: {}", instruction))]
+ InvalidInstruction { instruction: String },
+ #[snafu(display("Invalid argument given: {}", argument))]
+ InvalidArgument { argument: String },
+ #[snafu(display("Unparseable line: {}", line))]
+ InvalidLine { line: String },
+}
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub enum Instruction {
+ Accumulate,
+ Jump,
+ NoOperation,
+}
+
+pub struct Emulator {
+ accumulator: i64,
+ program_counter: usize,
+}
+
+impl Emulator {
+ pub fn new() -> Self {
+ Self {
+ accumulator: 0,
+ program_counter: 0,
+ }
+ }
+
+ pub fn reset(&mut self) {
+ self.accumulator = 0;
+ self.program_counter = 0;
+ }
+
+ pub fn execute_instruction(
+ &mut self,
+ instruction: Instruction,
+ argument: i64,
+ ) -> Result<(), EmulatorError> {
+ match instruction {
+ Instruction::Accumulate => self.accumulator += argument,
+ Instruction::Jump => {
+ self.program_counter = self.program_counter.wrapping_add(argument as usize - 1)
+ }
+ Instruction::NoOperation => {}
+ }
+
+ Ok(())
+ }
+
+ pub fn run_program_finitely(&mut self, program: &Program) -> Result<i64, EmulatorError> {
+ let mut executed = HashSet::new();
+
+ loop {
+ let (instruction, argument) = program
+ .get(self.program_counter)
+ .ok_or(EmulatorError::SegmentationFault)?;
+ executed.insert(self.program_counter);
+
+ self.execute_instruction(*instruction, *argument)?;
+
+ self.program_counter += 1;
+
+ if executed.contains(&self.program_counter) {
+ break Err(EmulatorError::InfiniteLoop {
+ accumulator: self.accumulator,
+ });
+ } else if self.program_counter >= program.len() {
+ break Ok(self.accumulator);
+ }
+ }
+ }
+}
+
+pub fn parse_code(input: &str) -> Result<Program, ProgramParseError> {
+ input
+ .lines()
+ .map(|instruction| {
+ let (name, argument): (&str, &str) = {
+ let temp: Vec<&str> = instruction.split(' ').collect();
+ if temp.len() != 2 {
+ Err(ProgramParseError::InvalidLine {
+ line: instruction.to_string(),
+ })
+ } else {
+ Ok((temp[0], temp[1]))
+ }
+ }?;
+
+ Ok((
+ match name {
+ "acc" => Instruction::Accumulate,
+ "jmp" => Instruction::Jump,
+ "nop" => Instruction::NoOperation,
+ _ => Err(ProgramParseError::InvalidInstruction {
+ instruction: name.to_string(),
+ })?,
+ },
+ argument
+ .parse()
+ .or(Err(ProgramParseError::InvalidArgument {
+ argument: argument.to_string(),
+ }))?,
+ ))
+ })
+ .collect()
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use indoc::indoc;
+
+ #[test]
+ fn test_parsing() -> Result<(), Box<dyn std::error::Error>> {
+ let input = indoc!(
+ "nop +0
+ acc +1
+ jmp +4
+ acc +3
+ jmp -3
+ acc -99
+ acc +1
+ jmp -4
+ acc +6
+ "
+ );
+
+ let code = parse_code(&input)?;
+ assert_eq!(
+ code,
+ vec![
+ (Instruction::NoOperation, 0),
+ (Instruction::Accumulate, 1),
+ (Instruction::Jump, 4),
+ (Instruction::Accumulate, 3),
+ (Instruction::Jump, -3),
+ (Instruction::Accumulate, -99),
+ (Instruction::Accumulate, 1),
+ (Instruction::Jump, -4),
+ (Instruction::Accumulate, 6),
+ ]
+ );
+
+ Ok(())
+ }
+
+ #[test]
+ fn test_running() -> Result<(), Box<dyn std::error::Error>> {
+ let input = indoc!(
+ "nop +0
+ acc +1
+ jmp +4
+ acc +3
+ jmp -3
+ acc -99
+ acc +1
+ jmp -4
+ acc +6
+ "
+ );
+
+ let code = parse_code(&input)?;
+ let mut emulator = Emulator::new();
+ assert_eq!(
+ emulator.run_program_finitely(&code),
+ Err(EmulatorError::InfiniteLoop { accumulator: 5 })
+ );
+
+ Ok(())
+ }
+}
diff --git a/day-8/src/main.rs b/day-8/src/main.rs
new file mode 100644
index 0000000..e4afef8
--- /dev/null
+++ b/day-8/src/main.rs
@@ -0,0 +1,49 @@
+use std::fs;
+
+mod emulator;
+
+use emulator::{parse_code, Emulator, EmulatorError, Instruction};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+ let input = fs::read_to_string("input")?;
+ let program = parse_code(&input)?;
+
+ // Part 1
+ let mut emulator = Emulator::new();
+ if let Err(EmulatorError::InfiniteLoop { accumulator }) =
+ emulator.run_program_finitely(&program)
+ {
+ println!("{}", accumulator);
+ } else {
+ panic!("We should get an infinite loop.");
+ }
+
+ // Part 2
+ let result = program
+ .iter()
+ .enumerate()
+ .filter_map(|(i, instruction)| match instruction {
+ (Instruction::Jump, arg) => {
+ let mut program = program.clone();
+ program[i] = (Instruction::NoOperation, *arg);
+ emulator.reset();
+ emulator.run_program_finitely(&program).ok()
+ }
+ (Instruction::NoOperation, arg) => {
+ let mut program = program.clone();
+ program[i] = (Instruction::Jump, *arg);
+ emulator.reset();
+ emulator.run_program_finitely(&program).ok()
+ }
+ (_, _) => None,
+ })
+ .next();
+
+ if let Some(result) = result {
+ println!("{}", result);
+ } else {
+ panic!("We should have at least one non-infinte loop.");
+ }
+
+ Ok(())
+}