Added Solution for 2020 day 08

2020/day08_handheld_halting/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day08_handheld_halting"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2020/day08_handheld_halting/challenge.txt

@@ -0,0 +1,104 @@
+Your flight to the major airline hub reaches cruising altitude without incident. While you consider checking the in-flight menu for one of those drinks that come with a little umbrella, you are interrupted by the kid sitting next to you.
+
+Their [handheld game console](https://en.wikipedia.org/wiki/Handheld_game_console) won't turn on! They ask if you can take a look.
+
+You narrow the problem down to a strange *infinite loop* in the boot code (your puzzle input) of the device. You should be able to fix it, but first you need to be able to run the code in isolation.
+
+The boot code is represented as a text file with one *instruction* per line of text. Each instruction consists of an *operation* (`acc`, `jmp`, or `nop`) and an *argument* (a signed number like `+4` or `-20`).
+
+* `acc` increases or decreases a single global value called the *accumulator* by the value given in the argument. For example, `acc +7` would increase the accumulator by 7. The accumulator starts at `0`. After an `acc` instruction, the instruction immediately below it is executed next.
+* `jmp` *jumps* to a new instruction relative to itself. The next instruction to execute is found using the argument as an *offset* from the `jmp` instruction; for example, `jmp +2` would skip the next instruction, `jmp +1` would continue to the instruction immediately below it, and `jmp -20` would cause the instruction 20 lines above to be executed next.
+* `nop` stands for *No OPeration* - it does nothing. The instruction immediately below it is executed next.
+
+For example, consider the following program:
+
+```
+nop +0
+acc +1
+jmp +4
+acc +3
+jmp -3
+acc -99
+acc +1
+jmp -4
+acc +6
+
+```
+
+These instructions are visited in this order:
+
+```
+nop +0  | 1
+acc +1  | 2, 8(!)
+jmp +4  | 3
+acc +3  | 6
+jmp -3  | 7
+acc -99 |
+acc +1  | 4
+jmp -4  | 5
+acc +6  |
+
+```
+
+First, the `nop +0` does nothing. Then, the accumulator is increased from 0 to 1 (`acc +1`) and `jmp +4` sets the next instruction to the other `acc +1` near the bottom. After it increases the accumulator from 1 to 2, `jmp -4` executes, setting the next instruction to the only `acc +3`. It sets the accumulator to 5, and `jmp -3` causes the program to continue back at the first `acc +1`.
+
+This is an *infinite loop*: with this sequence of jumps, the program will run forever. The moment the program tries to run any instruction a second time, you know it will never terminate.
+
+Immediately *before* the program would run an instruction a second time, the value in the accumulator is *`5`*.
+
+Run your copy of the boot code. Immediately before any instruction is executed a second time, *what value is in the accumulator?*
+
+Your puzzle answer was `2080`.
+
+\--- Part Two ---
+----------
+
+After some careful analysis, you believe that *exactly one instruction is corrupted*.
+
+Somewhere in the program, *either* a `jmp` is supposed to be a `nop`, *or* a `nop` is supposed to be a `jmp`. (No `acc` instructions were harmed in the corruption of this boot code.)
+
+The program is supposed to terminate by *attempting to execute an instruction immediately after the last instruction in the file*. By changing exactly one `jmp` or `nop`, you can repair the boot code and make it terminate correctly.
+
+For example, consider the same program from above:
+
+```
+nop +0
+acc +1
+jmp +4
+acc +3
+jmp -3
+acc -99
+acc +1
+jmp -4
+acc +6
+
+```
+
+If you change the first instruction from `nop +0` to `jmp +0`, it would create a single-instruction infinite loop, never leaving that instruction. If you change almost any of the `jmp` instructions, the program will still eventually find another `jmp` instruction and loop forever.
+
+However, if you change the second-to-last instruction (from `jmp -4` to `nop -4`), the program terminates! The instructions are visited in this order:
+
+```
+nop +0  | 1
+acc +1  | 2
+jmp +4  | 3
+acc +3  |
+jmp -3  |
+acc -99 |
+acc +1  | 4
+nop -4  | 5
+acc +6  | 6
+
+```
+
+After the last instruction (`acc +6`), the program terminates by attempting to run the instruction below the last instruction in the file. With this change, after the program terminates, the accumulator contains the value *`8`* (`acc +1`, `acc +1`, `acc +6`).
+
+Fix the program so that it terminates normally by changing exactly one `jmp` (to `nop`) or `nop` (to `jmp`). *What is the value of the accumulator after the program terminates?*
+
+Your puzzle answer was `2477`.
+
+Both parts of this puzzle are complete! They provide two gold stars: \*\*
+
+At this point, you should [return to your Advent calendar](/2020) and try another puzzle.
+
+If you still want to see it, you can [get your puzzle input](8/input).

2020/day08_handheld_halting/src/lib.rs

@@ -0,0 +1,133 @@
+use core::fmt::Display;
+use std::{num::ParseIntError, collections::HashSet};
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum ParseError {
+    ParseIntError(std::num::ParseIntError),
+    LineMalformed(String),
+}
+
+impl From<ParseIntError> for ParseError {
+    fn from(value: ParseIntError) -> Self {
+        Self::ParseIntError(value)
+    }
+}
+
+impl Display for ParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::ParseIntError(e) => write!(f, "Unable to parse into integer: {e}"),
+            Self::LineMalformed(v) => write!(f, "Line is malformed: {v}"),
+        }
+    }
+}
+
+#[derive(Clone)]
+enum Instruction {
+    Acc(isize),
+    Jmp(isize),
+    Nop(isize),
+}
+
+impl TryFrom<&str> for Instruction {
+    type Error = ParseError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        let parts: Vec<_> = value.split_whitespace().collect();
+        if parts.len() == 2 {
+            let argument = if parts[1].starts_with('+') {
+                parts[1][1..].parse::<isize>()?
+            } else {
+                parts[1].parse::<isize>()?
+            };
+            match parts[0] {
+                "acc" => Ok(Self::Acc(argument)),
+                "jmp" => Ok(Self::Jmp(argument)),
+                "nop" => Ok(Self::Nop(argument)),
+                _ => Err(Self::Error::LineMalformed(value.to_string())),
+            }
+        } else {
+            Err(Self::Error::LineMalformed(value.to_string()))
+        }
+    }
+}
+
+#[derive(Default, Clone)]
+struct Cpu {
+    program: Vec<Instruction>,
+    next_instr: usize,
+    accumulator: isize,
+    visited: HashSet<usize>,
+}
+
+impl TryFrom<&str> for Cpu {
+    type Error = ParseError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        let program: Vec<_> = value.lines().map(Instruction::try_from).collect::<Result<Vec<_>, _>>()?;
+        Ok(Self { program, ..Default::default() })
+    }
+}
+
+impl Cpu {
+    fn run_until_loop(&mut self) -> Result<isize, isize> {
+        match self.program[self.next_instr] {
+            Instruction::Acc(i) => {
+                self.accumulator += i;
+                self.next_instr += 1;
+            },
+            Instruction::Jmp(p) if p >= 0 => self.next_instr += p.unsigned_abs(),
+            Instruction::Jmp(n) => self.next_instr -= n.unsigned_abs(),
+            Instruction::Nop(_) => self.next_instr += 1,
+        }
+        if self.visited.contains(&self.next_instr) {
+            Err(self.accumulator)
+        } else if self.next_instr == self.program.len() {
+            Ok(self.accumulator)
+        } else {
+            self.visited.insert(self.next_instr);
+            self.run_until_loop()
+        }
+    }
+}
+
+pub fn run(input: &str) -> Result<(isize, isize), ParseError> {
+    let cpu = Cpu::try_from(input)?;
+    let mut cpu_1 = cpu.clone();
+    let first = cpu_1.run_until_loop().err().unwrap();
+    for i in 0..cpu.program.len() {
+        let new = match cpu.program[i] {
+            Instruction::Acc(_) => continue,
+            Instruction::Jmp(i) => Instruction::Nop(i),
+            Instruction::Nop(i) => Instruction::Jmp(i),
+        };
+        let mut cpu_2 = cpu.clone();
+        cpu_2.program[i] = new;
+        if let Ok(second) = cpu_2.run_until_loop() {
+            return Ok((first, second));
+        }
+    }
+    panic!("No way found to break the infinite loop");
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::read_to_string;
+
+    fn read_file(name: &str) -> String {
+        read_to_string(name).expect(&format!("Unable to read file: {name}")[..]).trim().to_string()
+    }
+
+    #[test]
+    fn test_sample() {
+        let sample_input = read_file("tests/sample_input");
+        assert_eq!(run(&sample_input), Ok((5, 8)));
+    }
+
+    #[test]
+    fn test_challenge() {
+        let challenge_input = read_file("tests/challenge_input");
+        assert_eq!(run(&challenge_input), Ok((2080, 2477)));
+    }
+}

2020/day08_handheld_halting/tests/challenge_input

@@ -0,0 +1,641 @@
+acc -8
+acc +19
+nop +178
+jmp +493
+acc +7
+jmp +267
+jmp +604
+acc +30
+acc +11
+acc -17
+nop +402
+jmp +81
+acc +20
+acc +19
+acc +36
+jmp +6
+acc +43
+acc +6
+acc +10
+nop +326
+jmp +228
+nop +371
+acc +49
+nop +140
+acc -11
+jmp +3
+nop +366
+jmp +74
+nop +229
+jmp +554
+acc +12
+acc +6
+jmp +163
+acc +43
+acc +23
+jmp +310
+acc -6
+nop +341
+acc +50
+acc +44
+jmp +378
+acc +28
+acc +29
+nop +76
+jmp +136
+nop +445
+acc +27
+acc -8
+acc +34
+jmp +199
+acc +39
+acc +25
+acc -14
+acc +1
+jmp +189
+acc +2
+acc -9
+jmp -7
+acc +28
+acc +28
+jmp +458
+jmp +1
+nop +299
+jmp +427
+acc +10
+acc +32
+jmp +340
+acc +26
+jmp +563
+jmp +1
+acc +9
+jmp +42
+acc +4
+jmp +468
+acc +1
+acc +3
+jmp +258
+acc +29
+acc +7
+acc -5
+jmp +288
+acc +22
+acc +32
+acc -6
+jmp +173
+acc +48
+acc +42
+acc +26
+jmp +380
+jmp +126
+acc +45
+jmp -27
+acc +50
+jmp +14
+jmp +472
+acc -19
+jmp +363
+acc +19
+acc -8
+acc +25
+jmp +450
+acc -7
+acc +27
+acc +44
+acc +17
+jmp +487
+jmp +89
+nop +216
+nop +345
+acc -1
+acc +37
+jmp +455
+jmp +294
+acc +20
+acc +38
+jmp +419
+acc +17
+acc +17
+jmp +125
+jmp +81
+acc +37
+acc -8
+acc +9
+acc +31
+jmp +218
+acc +24
+acc +28
+acc -4
+acc -12
+jmp -40
+acc +40
+nop +359
+nop +182
+nop +306
+jmp +296
+acc -8
+jmp +1
+nop +43
+acc -14
+jmp +239
+acc +13
+acc +10
+jmp +1
+jmp -36
+acc -16
+acc +2
+jmp +344
+jmp +442
+acc +35
+acc +2
+acc +27
+acc +17
+jmp -27
+nop +478
+acc +6
+acc +7
+jmp +454
+nop -145
+acc +20
+acc -6
+jmp +182
+nop +251
+jmp -37
+acc +26
+jmp +300
+acc +29
+acc +44
+acc +32
+nop +56
+jmp +31
+acc -16
+jmp +53
+acc -9
+jmp +84
+jmp +1
+nop +30
+acc -15
+jmp +262
+acc -19
+jmp +163
+jmp +441
+acc +27
+jmp +449
+acc +42
+acc +45
+acc +21
+acc +22
+jmp +338
+acc +24
+jmp +301
+acc +42
+acc +42
+acc +26
+jmp +348
+jmp +361
+acc -5
+acc -19
+acc +4
+jmp -117
+jmp +254
+jmp +1
+acc +47
+acc -3
+jmp +271
+jmp +388
+acc +2
+acc -17
+acc +37
+jmp -73
+acc +37
+acc +34
+jmp +1
+jmp -148
+jmp -56
+jmp +103
+acc -5
+acc +23
+acc +3
+jmp +405
+nop +255
+acc +14
+nop -41
+acc +12
+jmp +94
+acc +22
+acc +30
+jmp -107
+acc +12
+acc -2
+jmp +65
+acc +35
+acc -4
+jmp -174
+nop -159
+acc +47
+jmp -52
+acc +35
+jmp +73
+acc +1
+acc +19
+acc +35
+acc +15
+jmp -59
+jmp +312
+acc +20
+acc +25
+acc +45
+jmp -4
+acc -4
+nop -160
+acc -8
+acc +31
+jmp +166
+acc +20
+acc +16
+acc -1
+jmp +234
+acc +0
+jmp -45
+acc +47
+acc +17
+nop -187
+nop +206
+jmp +17
+acc +36
+acc +0
+acc +7
+jmp +263
+acc +32
+acc -6
+nop +35
+jmp -101
+acc +49
+nop -60
+jmp +118
+acc -1
+acc -7
+nop -94
+acc +21
+jmp +82
+nop +216
+acc +5
+nop -99
+jmp -47
+acc +31
+acc +2
+acc +26
+acc +27
+jmp -224
+acc +15
+acc +48
+jmp +220
+nop +152
+jmp -69
+acc +4
+acc +24
+jmp +200
+acc +14
+jmp +126
+acc +48
+acc +47
+acc +10
+jmp +26
+acc +16
+jmp -203
+acc +21
+jmp -158
+acc -15
+acc -13
+jmp -94
+jmp -136
+nop -247
+acc +16
+jmp -130
+acc +31
+jmp +115
+jmp -159
+acc +7
+acc +50
+jmp +52
+acc +22
+acc +26
+jmp +249
+acc -18
+jmp +1
+jmp -251
+nop +254
+jmp -127
+acc +37
+jmp -93
+nop +73
+acc +11
+acc +36
+jmp +277
+acc +29
+acc +16
+jmp -88
+nop +8
+acc +18
+acc +47
+acc -9
+jmp +184
+jmp -142
+acc +50
+jmp +287
+jmp -250
+jmp -296
+jmp -83
+acc +13
+acc +29
+acc +28
+acc +16
+jmp +40
+acc +33
+acc -13
+jmp +43
+nop +275
+acc +24
+nop -257
+nop -65
+jmp -112
+acc +4
+acc +38
+jmp -193
+jmp +1
+acc -18
+acc +15
+jmp -223
+acc -18
+jmp -55
+jmp -207
+acc -6
+jmp -215
+acc +16
+acc +44
+jmp +1
+acc +47
+jmp -35
+acc +47
+acc +47
+acc +35
+jmp +144
+jmp +1
+acc +45
+acc +25
+jmp -293
+acc +32
+jmp -381
+nop +65
+jmp +1
+acc +2
+jmp -74
+acc -13
+acc -9
+acc +4
+jmp -251
+jmp +1
+jmp +71
+acc -12
+acc +7
+acc +15
+jmp +11
+jmp -68
+acc +33
+jmp -330
+jmp +48
+acc -15
+acc -11
+jmp +97
+acc -9
+acc -10
+jmp +100
+acc +29
+acc +21
+jmp -134
+acc -18
+acc +38
+jmp +67
+jmp -12
+acc +27
+acc +26
+acc -8
+acc -2
+jmp -124
+jmp +165
+nop -245
+acc -16
+acc +25
+acc -19
+jmp -328
+nop -182
+acc -7
+acc +46
+jmp -250
+acc +45
+acc -7
+nop -256
+acc -2
+jmp +21
+acc +21
+acc +37
+jmp +156
+nop +32
+jmp -195
+nop -355
+acc -14
+nop -302
+acc +48
+jmp -407
+acc +50
+acc -9
+acc +47
+jmp -110
+acc +31
+acc +37
+acc +15
+jmp -162
+acc -14
+jmp -437
+acc +44
+jmp +1
+acc +24
+jmp -139
+jmp -362
+acc +40
+jmp -41
+acc +38
+jmp -231
+acc +31
+acc +23
+jmp +135
+acc -19
+acc +15
+jmp +148
+acc +16
+acc -18
+acc -3
+acc +1
+jmp -189
+acc -12
+acc -6
+acc -18
+nop -454
+jmp +83
+nop -190
+jmp -17
+acc -7
+acc +34
+acc -1
+jmp +94
+acc +42
+jmp +34
+nop -150
+nop +90
+nop -126
+jmp -161
+acc +5
+acc +11
+acc +20
+acc +38
+jmp -97
+acc +49
+acc +29
+acc +26
+jmp -36
+acc +4
+acc -14
+acc +30
+acc +42
+jmp -192
+jmp -336
+acc +34
+acc +31
+acc +2
+acc +33
+jmp +65
+acc +4
+jmp -459
+nop -399
+acc -6
+nop -256
+jmp -420
+acc -12
+acc -17
+jmp -276
+acc +45
+acc +40
+jmp -180
+acc +50
+jmp -501
+acc +17
+jmp -232
+acc +12
+jmp -109
+nop -291
+nop -345
+jmp +100
+acc +36
+acc +2
+acc -2
+jmp +1
+acc +23
+nop -299
+acc +24
+acc +30
+jmp -476
+acc +0
+acc +6
+acc +49
+jmp +6
+nop -461
+jmp -539
+nop -62
+acc +48
+jmp -526
+jmp -365
+acc +47
+acc +10
+acc +32
+jmp -490
+nop -148
+acc +42
+acc +5
+jmp -358
+acc -5
+jmp -101
+jmp -502
+acc +15
+acc +45
+nop -399
+jmp +1
+acc +31
+acc +47
+acc +49
+jmp -269
+acc +6
+acc +45
+acc -8
+acc -6
+jmp +36
+jmp +51
+acc +39
+jmp -64
+acc +47
+jmp +1
+acc -8
+jmp -102
+acc -8
+jmp -202
+jmp -18
+acc +1
+jmp -484
+acc +35
+acc +30
+acc +49
+jmp -562
+jmp -515
+acc -13
+nop -6
+jmp -369
+acc +27
+acc +18
+nop -477
+acc -10
+jmp -430
+jmp +1
+acc +7
+nop -111
+jmp -445
+jmp +12
+jmp -50
+acc +7
+acc +3
+nop -433
+jmp -390
+acc -5
+acc +50
+jmp -67
+acc +45
+acc -10
+jmp -446
+jmp -496
+jmp -17
+acc +14
+acc +33
+jmp -239
+acc +3
+acc -3
+acc +27
+acc -3
+jmp -162
+jmp -16
+acc +23
+acc +26
+acc +25
+jmp -346
+acc +40
+acc +45
+acc +42
+acc -4
+jmp +1

2020/day08_handheld_halting/tests/sample_input

@@ -0,0 +1,9 @@
+nop +0
+acc +1
+jmp +4
+acc +3
+jmp -3
+acc -99
+acc +1
+jmp -4
+acc +6