day17.rs

use std::io::{BufReader, BufRead};
use std::fs::File;
use std::collections::HashMap;


struct Machine {
    prog_ptr: i64,
    relative_base: i64,
    program: Vec<i64>,
    input: Vec<i64>,
    output: Vec<i64>,
    state: MachineState
}

#[derive(PartialEq)]
enum MachineState {
    ReadyToRun,
    WaitingForInput,
    OutputAvailable,
    Terminated
}

enum InstructionResult {
    Continue,
    WaitForInput,
    OutputDelivered,
    Invalid,
    Exit
}

enum ParameterMode {
    Position = 0,
    Direct = 1,
    Relative= 2
}

impl Machine {
    fn resume(&mut self) {
        loop {
            let a = self.run_one_instruction();
            match a {
                InstructionResult::Continue => { self.state = MachineState::ReadyToRun },
                InstructionResult::WaitForInput => { self.state = MachineState::WaitingForInput; break; },
                InstructionResult::OutputDelivered => { self.state = MachineState::OutputAvailable; break; },
                InstructionResult::Exit => { self.state = MachineState::Terminated; break; },
                _ => panic!("Unexpected action."),
            }
        }    
    }

    fn grow_storage_if_required(&mut self, location: i64) {
        if location >= self.program.len() as i64 {
            self.program.resize((location + 1) as usize, 0)
        }
    }

    fn get(&mut self, location: i64) -> i64 {
        self.grow_storage_if_required(location);
        self.program[location as usize]
    }

    fn put(&mut self, location: i64, value: i64) {
        self.grow_storage_if_required(location);
        self.program[location as usize] = value;
    }

    fn next_cell(&mut self) -> i64 {
        let ind = self.prog_ptr;
        self.prog_ptr += 1;
        self.get(ind)
    }

    fn get_parameter_value(&mut self, mode: i64) -> i64 {
        let value = self.next_cell();
        if mode == ParameterMode::Position as i64 {
            return self.get(value)
        } else if mode == ParameterMode::Direct as i64 {
            return value
        } else if mode == ParameterMode::Relative as i64 {
            return self.get(value + self.relative_base)
        } else {
            panic!("Unknown parameter mode: {}", mode)
        }
    }

    fn get_storage_location(&mut self, mode: i64) -> i64 {
        if mode == ParameterMode::Relative as i64 {
            self.next_cell() + self.relative_base
        } else {
            self.next_cell()
        }
    }

    const ADD: i64 =  1;
    const MULT: i64 =  2;
    const INPUT: i64 = 3;
    const OUTPUT: i64 = 4;
    const JUMP_TRUE: i64 = 5;
    const JUMP_FALSE: i64 = 6;
    const LESS_THAN: i64 = 7;
    const EQUALS: i64 = 8;
    const RELATIVE_BASE_OFFSET: i64 = 9;
    const EXIT: i64 =  99;

    fn run_one_instruction(&mut self) -> InstructionResult {
        let saved_prog_ptr = self.prog_ptr;
        let next_instruction_code = self.next_cell();
        let next_op_code = next_instruction_code % 100;
        let mode_par_1 =  (next_instruction_code / 100) % 10;
        let mode_par_2 = (next_instruction_code / 1000) % 10;
        let mode_par_3 = (next_instruction_code / 10000) % 10;
        match next_op_code {
            Machine::ADD => {
                let t1 = self.get_parameter_value(mode_par_1);
                let t2 = self.get_parameter_value(mode_par_2);
                let store_at = self.get_storage_location(mode_par_3);
                self.put(store_at, t1 + t2);
                InstructionResult::Continue
            },
            Machine::MULT => {
                let f1 = self.get_parameter_value(mode_par_1);
                let f2 = self.get_parameter_value(mode_par_2);
                let store_at = self.get_storage_location(mode_par_3);
                self.put(store_at, f1 * f2);
                InstructionResult::Continue
            },
            Machine::INPUT => {
                if !self.input.is_empty() {
                    let store_at = self.get_storage_location(mode_par_1);
                    let c = self.input.remove(0);
                    self.put(store_at, c);
                    InstructionResult::Continue
                } else {
                    self.prog_ptr = saved_prog_ptr;
                    InstructionResult::WaitForInput
                }
            },
            Machine::JUMP_TRUE => {
                let value = self.get_parameter_value(mode_par_1);
                let jump_target = self.get_parameter_value(mode_par_2);
                if value != 0 {
                    self.prog_ptr = jump_target
                }
                InstructionResult::Continue
            },
            Machine::JUMP_FALSE => {
                let value = self.get_parameter_value(mode_par_1);
                let jump_target = self.get_parameter_value(mode_par_2);
                if value == 0 {
                    self.prog_ptr = jump_target
                }
                InstructionResult::Continue
            },
            Machine::LESS_THAN => {
                let p1 = self.get_parameter_value(mode_par_1);
                let p2 = self.get_parameter_value(mode_par_2);
                let store_at = self.get_storage_location(mode_par_3);
                let result = if p1 < p2 { 1 } else { 0 };
                self.put(store_at, result);
                InstructionResult::Continue
            },
            Machine::EQUALS => {
                let p1 = self.get_parameter_value(mode_par_1);
                let p2 = self.get_parameter_value(mode_par_2);
                let store_at = self.get_storage_location(mode_par_3);
                let result = if p1 == p2 { 1 } else { 0 };
                self.put(store_at, result);
                InstructionResult::Continue
            },
            Machine::OUTPUT => {
                let v = self.get_parameter_value(mode_par_1);
                self.output.push(v);
                InstructionResult::OutputDelivered
            },
            Machine::RELATIVE_BASE_OFFSET => {
                let v = self.get_parameter_value(mode_par_1);
                self.relative_base += v;
                InstructionResult::Continue
            },
            Machine::EXIT => InstructionResult::Exit,
            _ => InstructionResult::Invalid
        }
    }    
}

fn load_program(program_file: &String) -> Vec<i64> {
    let mut prog: Vec<i64> = vec![];
    let file = File::open(program_file).expect("Could not open program file!");
    let reader = BufReader::new(file);

    let line = reader.lines().next().expect("Could not read from file");
    let line = line.expect("No string there.");
    for s in line.split(",") {
        let c = i64::from_str_radix(&s, 10).expect("Could not parse int");
        prog.push(c);
    }
    prog
}

fn part_1(program: &Vec<i64>) {
    let mut machine = Machine {
        prog_ptr: 0,
        relative_base: 0,
        program: program.clone(),
        input: vec!(),
        output: vec!(),
        state: MachineState::ReadyToRun
    };

    let mut area: HashMap<(i64, i64), char> = HashMap::new();
    let mut cx = 0;
    let mut cy = 0;

    loop {
        match machine.state {
            MachineState::Terminated => break,
            MachineState::OutputAvailable => {
                let code = machine.output.remove(0);
                if code == 10 {
                    cx = 0;
                    cy += 1;
                } else {    
                    let c = std::char::from_u32(code as u32).unwrap();
                    area.insert((cx, cy), c);
                    cx += 1;
                }
            },
            MachineState::WaitingForInput => {
                panic!("Unexpected input requested.")
            },
            MachineState::ReadyToRun => {},
        }
        machine.resume()
    }
    paint_area(&area);

    let intersections = find_intersections(&area);
    let summed_alignment = intersections.iter().fold(0, |acc, (x, y)| acc + x * y);

    println!("Solution part 1 = {}", summed_alignment);
}

fn part_2(program: &Vec<i64>) {
    //
    // Found by playing around with the full path in the text editor manually.
    //
    let ascii_input = "A,B,A,B,A,C,B,C,A,C\nR,4,L,10,L,10\nL,8,R,12,R,10,R,4\nL,8,L,8,R,10,R,4\nn\n";   

    let mut int_input: Vec<i64> = ascii_input.chars().map(|c| c as i64).collect();

    let mut program_part_2 = program.clone();
    program_part_2[0] = 2;
    let mut machine = Machine {
        prog_ptr: 0,
        relative_base: 0,
        program: program_part_2,
        input: vec!(),
        output: vec!(),
        state: MachineState::ReadyToRun
    };

    let mut last_output = -1;
    loop {
        match machine.state {
            MachineState::Terminated => break,
            MachineState::OutputAvailable => {
                last_output = machine.output.remove(0);
            },
            MachineState::WaitingForInput => {
                machine.input.push(int_input.remove(0));
            },
            MachineState::ReadyToRun => {},
        }
        machine.resume()
    }
    println!("Solution part 2 = {}", last_output);
}

fn main() {
    let program_file = "prog".to_string();
    let program: Vec<i64> = load_program(&program_file);
    part_1(&program);
    part_2(&program);
}

fn find_intersections(area: &HashMap<(i64, i64), char>) -> Vec<(i64, i64)> {
    let ((min_x, min_y), (max_x, max_y)) = find_dimensions(&area);
    area.iter().filter(
        |((x, y), v)| 
            **v == '#' && *x != min_x && *x != max_x && *y != min_y && *y != max_y &&
            *area.get(&(*x + 1, *y)).unwrap() == '#'  &&
            *area.get(&(*x - 1, *y)).unwrap() == '#'  &&
            *area.get(&(*x, *y + 1)).unwrap() == '#'  &&
            *area.get(&(*x, *y - 1)).unwrap() == '#'
    ).map(|(k, _)| *k).collect()
}

fn find_dimensions(area: &HashMap<(i64, i64), char>) -> ((i64, i64), (i64, i64)) {
    let min_x = area.keys().fold(0, |acc, k| std::cmp::min(acc, k.0));
    let max_x = area.keys().fold(0, |acc, k| std::cmp::max(acc, k.0));
    let min_y = area.keys().fold(0, |acc, k| std::cmp::min(acc, k.1));
    let max_y = area.keys().fold(0, |acc, k| std::cmp::max(acc, k.1));
    ((min_x, min_y), (max_x, max_y))
}

fn paint_area(area: &HashMap<(i64, i64), char>) {
    let ((min_x, min_y), (max_x, max_y)) = find_dimensions(&area);
    for y in min_y..=max_y {
        for x in min_x..=max_x {
                
            print!("{}", area.get(&(x, y)).unwrap())
        }
        println!();
    }
}