From 351b0eb897d7ede2273e3f48097231de3396f4d2 Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Sat, 23 Dec 2017 10:42:47 +0200
Subject: Day 23: Rewrite this assembly as a decent program...

---
 inputs/day_23.txt |  32 +++++++++++
 src/bin/day_23.rs | 162 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 194 insertions(+)
 create mode 100644 inputs/day_23.txt

diff --git a/inputs/day_23.txt b/inputs/day_23.txt
new file mode 100644
index 0000000..9d29443
--- /dev/null
+++ b/inputs/day_23.txt
@@ -0,0 +1,32 @@
+set b 99
+set c b
+jnz a 2
+jnz 1 5
+mul b 100
+sub b -100000
+set c b
+sub c -17000
+set f 1
+set d 2
+set e 2
+set g d
+mul g e
+sub g b
+jnz g 2
+set f 0
+sub e -1
+set g e
+sub g b
+jnz g -8
+sub d -1
+set g d
+sub g b
+jnz g -13
+jnz f 2
+sub h -1
+set g b
+sub g c
+jnz g 2
+jnz 1 3
+sub b -17
+jnz 1 -23
diff --git a/src/bin/day_23.rs b/src/bin/day_23.rs
index 1fc3eca..d199af0 100644
--- a/src/bin/day_23.rs
+++ b/src/bin/day_23.rs
@@ -1,6 +1,168 @@
 extern crate advent_of_code_2017;
 use advent_of_code_2017::*;
 
+use std::str::FromStr;
+
 fn main() {
     let args = AdventArgs::init();
+
+    if args.part == 1 {
+        let instructions: Vec<Instruction> = args.input.iter()
+            .map(|line| line.parse().unwrap())
+            .collect();
+
+        let mut program = Program::new(instructions.clone(), args.part == 1);
+        let mul_called = program.run();
+        println!("Mult called {} times", mul_called);
+    } else {
+        println!("Result is {}", run_as_rust());
+    }
+
+}
+
+fn to_register(c: char) -> usize {
+    (c as u32 - 'a' as u32) as usize
+}
+
+struct Program {
+    instructions: Vec<Instruction>,
+    registers: [i64; 8],
+    pc: i64
+}
+
+impl Program {
+    fn new(instructions: Vec<Instruction>, part1: bool) -> Program {
+        let mut reg = [0; 8];
+        if part1 == false {
+            reg[0] = 1;
+        }
+        Program {
+            instructions: instructions,
+            registers: reg,
+            pc: 0
+        }
+    }
+    fn run(&mut self) -> u32 {
+        use Instruction::*;
+        
+        let mut mul_called = 0;
+        
+        while self.pc >= 0 && (self.pc as usize) < self.instructions.len() {
+            let ins = self.instructions[self.pc as usize].clone();
+            
+            match ins {
+                Set(x, y) => {
+                    let y_val = self.get(y);
+                    self.set(x, y_val);
+                },
+                Sub(x, y) => {
+                    let x_val = self.get(x);
+                    let y_val = self.get(y);
+                    self.set(x, x_val - y_val);
+                },
+                Mul(x, y) => {
+                    let x_val = self.get(x);
+                    let y_val = self.get(y);
+                    self.set(x, x_val * y_val);
+                    mul_called += 1;
+                },
+                Jnz(x, y) => {
+                    if self.get(x) != 0 {
+                        self.pc = self.pc + self.get(y) - 1;
+                    }
+                },
+            }
+            self.pc += 1;
+        }
+
+        mul_called
+    }
+
+    fn get(&self, register: Data) -> i64 {
+        use Data::*;
+        match register {
+            Register(c) => self.registers[c],
+            Literal(i) => i
+        }
+    }
+
+    fn set(&mut self, register: Data, value: i64) {
+        use Data::*;
+        match register {
+            Register(c) => {
+                self.registers[c] = value;
+            },
+            _ => {}
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+enum Instruction {
+    Set(Data, Data),
+    Sub(Data, Data),
+    Mul(Data, Data),
+    Jnz(Data, Data)
+}
+
+impl FromStr for Instruction {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        use Instruction::*;
+        
+        let mut str_iter = s.split_whitespace();
+        let ins = str_iter.next();
+        let x = str_iter.next().map(|x| x.parse::<Data>());
+        let y = str_iter.next().map(|x| x.parse::<Data>());
+
+        match (ins, x, y) {
+            (Some("set"), Some(Ok(x)), Some(Ok(y))) => Ok(Set(x, y)),
+            (Some("sub"), Some(Ok(x)), Some(Ok(y))) => Ok(Sub(x, y)),
+            (Some("mul"), Some(Ok(x)), Some(Ok(y))) => Ok(Mul(x, y)),
+            (Some("jnz"), Some(Ok(x)), Some(Ok(y))) => Ok(Jnz(x, y)),
+            (_, _, _) => Err(format!("Unknown instruction {}", s))
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum Data {
+    Literal(i64),
+    Register(usize)
+}
+
+impl FromStr for Data {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        use Data::*;
+        
+        match (s.parse(), s.chars().next()) {
+            (Ok(num), _) => Ok(Literal(num)),
+            (Err(_), Some(c)) => Ok(Register(to_register(c))),
+            (_, _) => Err(format!("Invalid data {}", s))
+        }
+    }
+}
+
+
+fn run_as_rust() -> i64 {
+    let mut h: i64 = 0;   
+    let mut b: i64 = 99 * 100 + 100000;
+    let c: i64 = b + 17000;
+
+    while b <= c {
+        let f = (2..b).any(|d| {
+            b % d == 0
+        });
+
+        if f {
+            h += 1;
+        }
+
+        b += 17;
+    }
+    
+    h
 }
-- 
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