From 319d8bf80de4f61897b32f351be38d3cbd58b425 Mon Sep 17 00:00:00 2001
From: Glenn Griffin <ggriffiniii@gmail.com>
Date: Tue, 8 Dec 2020 05:55:13 -0800
Subject: [PATCH] day 8

---
 input/2020/day8.txt | 653 ++++++++++++++++++++++++++++++++++++++++++++
 src/day8.rs         | 147 ++++++++++
 src/lib.rs          |   1 +
 3 files changed, 801 insertions(+)
 create mode 100644 input/2020/day8.txt
 create mode 100644 src/day8.rs

diff --git a/input/2020/day8.txt b/input/2020/day8.txt
new file mode 100644
index 0000000..1f0d43c
--- /dev/null
+++ b/input/2020/day8.txt
@@ -0,0 +1,653 @@
+acc +9
+acc -2
+acc -12
+acc +33
+jmp +301
+nop +508
+jmp +216
+acc +27
+acc +35
+acc +43
+acc +31
+jmp +309
+acc +18
+acc -19
+acc +7
+jmp +44
+acc -13
+acc -17
+acc +31
+jmp +311
+nop +612
+jmp +143
+acc +22
+nop +85
+jmp +458
+acc -3
+jmp +13
+acc -19
+acc +27
+acc +12
+jmp +483
+acc +40
+acc +6
+jmp +128
+jmp +10
+acc +0
+acc -3
+acc -2
+jmp -11
+acc +43
+acc -12
+jmp +158
+acc +0
+jmp +240
+jmp +1
+acc +5
+acc +15
+jmp +187
+nop +563
+jmp +51
+acc -16
+jmp +158
+jmp +322
+acc +47
+nop -1
+jmp +299
+acc +26
+acc +25
+jmp +232
+jmp -9
+acc +15
+jmp +54
+jmp +558
+acc +7
+acc -7
+jmp +399
+nop +447
+jmp +71
+acc +26
+acc +46
+jmp +145
+acc +38
+acc +30
+acc +21
+jmp +263
+acc +10
+jmp +168
+acc +22
+nop +561
+jmp -26
+jmp +1
+acc -7
+jmp -5
+acc +28
+acc -6
+jmp +370
+jmp +94
+acc +50
+acc +42
+acc -9
+acc +30
+jmp +70
+acc +29
+jmp +166
+acc -5
+acc -18
+nop +84
+acc +2
+jmp +366
+jmp -40
+acc -4
+acc -15
+acc -1
+jmp +169
+jmp +1
+acc -4
+acc +0
+jmp -45
+nop -21
+nop +241
+acc -18
+acc +19
+jmp +26
+nop -51
+jmp +260
+acc +17
+jmp +428
+acc +6
+jmp +405
+acc +22
+acc +10
+nop +471
+jmp +352
+acc -6
+acc +48
+acc +7
+acc +3
+jmp +57
+acc -10
+acc +16
+acc +16
+acc +43
+jmp +432
+acc -5
+acc +0
+nop +339
+acc +49
+jmp +17
+acc +33
+nop +166
+acc -5
+jmp +392
+nop +246
+acc -7
+acc +21
+acc +30
+jmp +398
+acc +36
+acc +24
+acc -15
+acc -9
+jmp +114
+acc +19
+jmp +11
+acc +43
+nop +182
+jmp -129
+nop -29
+acc -6
+acc +2
+jmp +398
+jmp +78
+acc +36
+jmp +393
+acc +15
+nop -11
+acc -7
+acc -9
+jmp +76
+acc +0
+acc +27
+jmp +25
+acc +27
+nop -54
+jmp +458
+acc +3
+acc +29
+acc -4
+acc +43
+jmp +413
+acc +33
+acc +13
+jmp +382
+jmp -83
+acc +42
+acc +24
+jmp +64
+acc +23
+acc -13
+nop +110
+acc -5
+jmp +114
+jmp +113
+nop +112
+acc +26
+jmp -133
+jmp -12
+jmp +1
+jmp +330
+acc +25
+acc -1
+acc +30
+acc +42
+jmp -187
+jmp +1
+acc +20
+acc +35
+acc +36
+jmp -125
+jmp +165
+acc +28
+acc -17
+acc -12
+jmp +1
+jmp -120
+nop +1
+acc +2
+acc +26
+jmp +398
+acc +20
+acc -1
+jmp -127
+acc +36
+acc +14
+jmp +1
+jmp +331
+acc +50
+acc +1
+acc -10
+nop +159
+jmp -83
+jmp +374
+acc +17
+jmp +372
+acc +44
+nop -39
+jmp +228
+acc +17
+jmp +74
+acc +16
+acc +33
+acc -2
+jmp +152
+jmp +29
+acc +8
+acc +27
+nop +59
+jmp -32
+acc +28
+jmp -227
+nop -35
+jmp -168
+acc +13
+nop +390
+jmp -204
+acc +16
+acc +44
+jmp -230
+jmp +25
+acc +30
+jmp +383
+acc -11
+acc +38
+acc +11
+jmp +341
+acc +35
+acc +46
+acc -1
+jmp +94
+acc -4
+acc +12
+jmp +111
+jmp +133
+nop +283
+acc +13
+acc +37
+jmp +74
+nop -218
+jmp -178
+acc +46
+acc +25
+acc -5
+jmp -174
+acc +28
+acc +39
+acc +36
+acc +22
+jmp -172
+acc +19
+jmp -250
+nop +62
+acc +44
+nop +347
+acc +40
+jmp +345
+acc -3
+acc -13
+acc -11
+jmp +56
+jmp -180
+acc +17
+acc -4
+acc +46
+nop -165
+jmp +321
+acc -4
+jmp +1
+acc +9
+acc -12
+jmp -155
+acc +5
+jmp -96
+acc +0
+acc -2
+acc +38
+jmp +67
+acc -4
+nop -283
+acc +28
+jmp +324
+acc -9
+acc +43
+acc -1
+acc +9
+jmp -290
+acc +3
+acc +22
+nop +84
+acc -17
+jmp -210
+acc +7
+jmp -260
+nop -232
+nop +87
+acc +43
+acc +36
+jmp +96
+jmp +238
+acc +13
+acc -14
+acc +32
+acc +11
+jmp -146
+acc +13
+acc +37
+acc -10
+jmp +187
+acc +49
+acc +15
+jmp -234
+jmp -328
+jmp -136
+jmp +143
+jmp +1
+acc +27
+acc +22
+jmp +1
+jmp -5
+acc +30
+nop -7
+acc -6
+jmp -71
+acc -17
+acc +15
+jmp -52
+jmp -126
+acc -4
+jmp +151
+jmp +52
+nop -86
+acc +25
+jmp +187
+nop -22
+jmp -219
+acc +33
+nop -120
+acc +0
+jmp +215
+acc +46
+acc +38
+jmp +1
+jmp -262
+jmp +157
+acc -15
+acc +48
+acc +39
+acc +10
+jmp -137
+acc +47
+acc +50
+jmp -324
+nop +214
+acc +39
+jmp -178
+acc +49
+acc -10
+jmp -268
+jmp +50
+acc -14
+nop -100
+jmp +20
+acc +45
+acc -12
+acc -4
+jmp -208
+acc -19
+jmp -340
+acc +36
+nop -358
+acc +5
+jmp -348
+acc +47
+nop -18
+acc -12
+jmp -131
+acc +19
+acc +10
+acc +19
+acc +31
+jmp -164
+nop +162
+nop -260
+jmp +146
+acc +32
+acc -1
+nop -14
+jmp -192
+acc +3
+acc +31
+nop -185
+jmp -208
+jmp -69
+acc +43
+acc +43
+jmp -68
+acc -16
+acc +5
+acc -9
+jmp +126
+acc +33
+acc +2
+acc +34
+acc -9
+jmp -16
+acc +34
+acc -19
+jmp -266
+nop +135
+nop -389
+acc +33
+jmp -195
+acc +48
+jmp +1
+acc -12
+jmp +143
+nop -317
+acc -14
+nop -127
+acc +32
+jmp -372
+acc +24
+nop -41
+nop -42
+jmp -344
+acc +23
+nop +117
+nop +92
+acc +42
+jmp +143
+acc +48
+acc -6
+nop -272
+acc -13
+jmp -379
+acc -2
+acc +44
+acc +9
+jmp -369
+acc +6
+acc +25
+acc +34
+jmp -301
+nop -227
+acc +43
+jmp -141
+acc +12
+acc +41
+acc +17
+acc -11
+jmp +29
+jmp -121
+acc +6
+acc +7
+acc +7
+jmp +131
+nop +144
+nop -142
+acc -13
+acc -18
+jmp +149
+acc +14
+acc +49
+acc +25
+acc -17
+jmp -9
+acc +26
+acc -4
+jmp -230
+acc -18
+acc +36
+acc +27
+nop -142
+jmp +21
+acc +34
+nop +54
+jmp -476
+acc +10
+jmp -174
+nop -354
+acc +1
+jmp -324
+acc +40
+jmp +94
+acc -12
+jmp -136
+nop -454
+acc -14
+jmp +116
+acc +12
+acc -1
+nop -453
+jmp -241
+jmp -479
+acc -19
+jmp -87
+acc +27
+acc +48
+acc +0
+jmp -476
+acc +16
+acc +46
+jmp -534
+acc +0
+jmp -344
+acc +0
+acc +28
+jmp +10
+jmp -248
+nop -186
+jmp +1
+acc +26
+jmp -153
+acc +14
+acc -8
+nop -416
+jmp -91
+jmp -409
+jmp -326
+acc +2
+acc +8
+acc -18
+acc +33
+jmp -468
+jmp -175
+acc -7
+acc +45
+jmp -18
+jmp -375
+acc -8
+jmp +28
+acc -16
+nop -38
+acc +37
+acc +48
+jmp -343
+acc +10
+acc +26
+acc -9
+acc -16
+jmp -348
+acc +37
+jmp -453
+acc -2
+acc +27
+acc +17
+acc +28
+jmp -406
+acc +25
+acc +24
+acc +44
+acc +44
+jmp -532
+acc +10
+jmp -531
+acc +39
+acc +40
+jmp -284
+acc +19
+acc +3
+nop -533
+acc -3
+jmp -162
+nop -438
+acc -5
+jmp -114
+acc +45
+acc +1
+acc +28
+acc +9
+jmp -550
+jmp -222
+jmp -106
+acc -7
+nop -263
+nop -375
+jmp -381
+acc -4
+nop -223
+jmp -171
+jmp -465
+acc -2
+nop -562
+jmp -190
+acc +40
+jmp -4
+acc +30
+acc +21
+jmp -435
+acc +1
+acc +10
+jmp +1
+jmp -157
+acc -7
+acc +18
+acc -3
+acc +24
+jmp -113
+acc +21
+jmp -339
+acc +34
+jmp -563
+acc +27
+jmp -589
+jmp -61
+acc +35
+acc +50
+acc +8
+jmp -553
+acc +48
+acc -15
+acc +29
+acc +24
+jmp +1
diff --git a/src/day8.rs b/src/day8.rs
new file mode 100644
index 0000000..e3ca719
--- /dev/null
+++ b/src/day8.rs
@@ -0,0 +1,147 @@
+use aoc_runner_derive::aoc;
+
+#[derive(Debug, Copy, Clone)]
+enum Instr {
+    Nop(isize),
+    Acc(isize),
+    Jmp(isize),
+}
+
+impl Instr {
+    fn parse(input: &str) -> Option<Instr> {
+        let space_idx = input.find(' ')?;
+        let (op, arg) = (&input[..space_idx], &input[space_idx + 1..]);
+        let arg = arg.parse().ok()?;
+        Some(match op {
+            "nop" => Instr::Nop(arg),
+            "acc" => Instr::Acc(arg),
+            "jmp" => Instr::Jmp(arg),
+            _ => return None,
+        })
+    }
+}
+
+#[derive(Debug, Clone)]
+struct BitSet(Vec<u64>);
+
+impl BitSet {
+    fn new(max_bits: usize) -> Self {
+        BitSet(vec![0; (max_bits - 1) / 64 + 1])
+    }
+
+    fn contains(&self, bit_idx: usize) -> bool {
+        let byte_idx = bit_idx / 64;
+        let bit_offset = bit_idx & 63;
+        self.0[byte_idx] & (1 << bit_offset) != 0
+    }
+
+    fn insert(&mut self, bit_idx: usize) {
+        let byte_idx = bit_idx / 64;
+        let bit_offset = bit_idx & 63;
+        self.0[byte_idx] |= 1 << bit_offset;
+    }
+}
+
+fn run_program(
+    program: &[Instr],
+    mut prev_instrs: BitSet,
+    mut pc: usize,
+    mut accum: isize,
+) -> (usize, isize) {
+    while pc < program.len() {
+        if prev_instrs.contains(pc) {
+            return (pc, accum);
+        }
+        let (new_pc, new_accum) = step(program[pc], &mut prev_instrs, pc, accum);
+        pc = new_pc;
+        accum = new_accum;
+    }
+    (pc, accum)
+}
+
+fn step(
+    instr: Instr,
+    mut prev_instrs: &mut BitSet,
+    mut pc: usize,
+    mut accum: isize,
+) -> (usize, isize) {
+    prev_instrs.insert(pc);
+    pc = match instr {
+        Instr::Nop(_) => pc + 1,
+        Instr::Acc(arg) => {
+            accum += arg;
+            pc + 1
+        }
+        Instr::Jmp(arg) => (pc as isize + arg) as usize,
+    };
+    (pc, accum)
+}
+
+#[aoc(day8, part1)]
+pub fn solve_d8_p1(input: &str) -> isize {
+    let program = input
+        .split('\n')
+        .map(|line| Instr::parse(line))
+        .collect::<Option<Vec<_>>>()
+        .unwrap();
+    run_program(&program, BitSet::new(program.len()), 0, 0).1
+}
+
+#[aoc(day8, part2)]
+pub fn solve_d8_p2(input: &str) -> isize {
+    let mut program = input
+        .split('\n')
+        .map(|line| Instr::parse(line))
+        .collect::<Option<Vec<_>>>()
+        .unwrap();
+    let mut pc = 0;
+    let mut accum = 0;
+    let mut prev_instrs = BitSet::new(program.len());
+    loop {
+        match program[pc] {
+            Instr::Nop(arg) => {
+                program[pc] = Instr::Jmp(arg);
+                let (new_pc, new_accum) = run_program(&program, prev_instrs.clone(), pc, accum);
+                if new_pc == program.len() {
+                    return new_accum;
+                }
+                program[pc] = Instr::Nop(arg);
+            }
+            Instr::Jmp(arg) => {
+                program[pc] = Instr::Nop(arg);
+                let (new_pc, new_accum) = run_program(&program, prev_instrs.clone(), pc, accum);
+                if new_pc == program.len() {
+                    return new_accum;
+                }
+                program[pc] = Instr::Jmp(arg);
+            }
+            _ => {}
+        }
+        let (new_pc, new_accum) = step(program[pc], &mut prev_instrs, pc, accum);
+        pc = new_pc;
+        accum = new_accum;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_bitset() {
+        let mut bs = BitSet::new(192);
+        for bit in 0..191 {
+            assert!(!bs.contains(bit));
+        }
+        bs.insert(5);
+        assert!(bs.contains(5));
+        bs.insert(191);
+        assert!(bs.contains(191));
+        bs.insert(63);
+        assert!(bs.contains(63));
+        bs.insert(64);
+        assert!(bs.contains(64));
+        bs.insert(65);
+        assert!(bs.contains(65));
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 5fede06..f230e09 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,5 +5,6 @@ pub mod day4;
 pub mod day5;
 pub mod day6;
 pub mod day7;
+pub mod day8;
 
 aoc_runner_derive::aoc_lib! { year = 2020 }