From aa33f429359d6b07f072d092dbdc1568de0adad1 Mon Sep 17 00:00:00 2001
From: inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>
Date: Sun, 13 Dec 2020 02:20:44 +0100
Subject: [PATCH] Solution for day 8

---
 day08/Cargo.toml  |  11 +++++
 day08/src/main.rs | 120 ++++++++++++++++++++++++++++++++++++++++++++++
 day09/src/main.rs |   1 -
 3 files changed, 131 insertions(+), 1 deletion(-)
 create mode 100644 day08/Cargo.toml
 create mode 100644 day08/src/main.rs

diff --git a/day08/Cargo.toml b/day08/Cargo.toml
new file mode 100644
index 0000000..4607d27
--- /dev/null
+++ b/day08/Cargo.toml
@@ -0,0 +1,11 @@
+[package]
+name = "day08"
+version = "0.1.0"
+authors = ["inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+lazy_static = "1.4.0"
+regex = "1"
diff --git a/day08/src/main.rs b/day08/src/main.rs
new file mode 100644
index 0000000..d5dce67
--- /dev/null
+++ b/day08/src/main.rs
@@ -0,0 +1,120 @@
+use std::collections::HashSet;
+use std::io::{self, BufRead};
+use std::error::Error;
+use std::str::FromStr;
+
+#[macro_use] extern crate lazy_static;
+use regex::Regex;
+
+#[derive(Clone, Copy)]
+enum Instruction {
+    Accumulate(i64),
+    Jump(i64),
+    NoOp(i64),
+}
+
+impl FromStr for Instruction {
+    type Err = Box<dyn Error>;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        lazy_static! {
+            static ref LINE_RE: Regex = Regex::new(r"^(\w+)\s+([+-]?\d+)$").unwrap();
+        }
+
+        match LINE_RE.captures(s) {
+            Some(captures) => {
+                match captures[1].as_ref() {
+                    "acc" => Ok(Self::Accumulate(captures[2].parse()?)),
+                    "jmp" => Ok(Self::Jump(captures[2].parse()?)),
+                    "nop" => Ok(Self::NoOp(captures[2].parse()?)),
+                    _ => Err(Box::from("wrong command")),
+                }
+            },
+            _ => Err(Box::from("wrong string format"))
+        }
+    }
+}
+
+enum ProgramResult {
+    Terminated(i64),
+    Looped(i64),
+}
+
+struct Program<'a> {
+    instructions: &'a[Instruction],
+    override_index: i64,
+}
+
+impl<'a> Program<'a> {
+    pub fn new(instructions: &'a [Instruction], override_index: i64) -> Self {
+        Program {
+            instructions,
+            override_index,
+        }
+    }
+
+    fn get_instruction(&self, index: i64) -> Option<Instruction> {
+        if index < 0 || (index as usize) >= self.instructions.len() {
+            return None;
+        }
+
+        if index != self.override_index {
+            return Some(self.instructions[index as usize]);
+        }
+
+        match self.instructions[index as usize] {
+            Instruction::Accumulate(value) => Some(Instruction::Accumulate(value)),
+            Instruction::Jump(ignore) => Some(Instruction::NoOp(ignore)),
+            Instruction::NoOp(offset) => Some(Instruction::Jump(offset)),
+        }
+    }
+
+    pub fn run(&self) -> ProgramResult {
+        let mut current_instruction_index = 0;
+        let mut visited_instructions = HashSet::new();
+        let mut accumulator = 0;
+        loop {
+            if visited_instructions.contains(&current_instruction_index) {
+                return ProgramResult::Looped(accumulator);
+            }
+    
+            visited_instructions.insert(current_instruction_index);
+    
+            match self.get_instruction(current_instruction_index) {
+                Some(Instruction::Accumulate(value)) => {
+                    accumulator += value;
+                },
+                Some(Instruction::Jump(offset)) => {
+                    current_instruction_index += offset-1;
+                }
+                Some(Instruction::NoOp(_)) => {},
+                None => {
+                    return ProgramResult::Terminated(accumulator);
+                }
+            }
+            
+            current_instruction_index += 1;
+        }
+        }
+}
+
+fn main() {
+    let stdin = io::stdin();
+    let instructions: Vec<_> = stdin.lock().lines().into_iter()
+        .map(|line| line.unwrap().parse::<Instruction>().unwrap())
+        .collect();
+
+    let program = Program::new(&instructions, -1);
+    match program.run() {
+        ProgramResult::Looped(accumulator) => println!("Original program looped: {}", accumulator),
+        ProgramResult::Terminated(accumulator) => println!("Original program terminated: {}", accumulator),
+    }
+
+    for i in 0..instructions.len() {
+        let program = Program::new(&instructions, i as i64);
+        match program.run() {
+            ProgramResult::Looped(_) => {},
+            ProgramResult::Terminated(accumulator) => println!("Program #{} terminated: {}", i, accumulator),
+        }
+    }
+}
diff --git a/day09/src/main.rs b/day09/src/main.rs
index 3367ded..e1a17aa 100644
--- a/day09/src/main.rs
+++ b/day09/src/main.rs
@@ -1,4 +1,3 @@
-use std::collections::HashMap;
 use std::io::{self, BufRead};
 
 const BLOCK_SIZE: usize = 25;