Year 2019 Day 19

Author: maneatingape

README.md

@@ -211,6 +211,7 @@ pie
 | 16 | [Flawed Frequency Transmission](https://adventofcode.com/2019/day/16) | [Source](src/year2019/day16.rs) | 4124 |
 | 17 | [Set and Forget](https://adventofcode.com/2019/day/17) | [Source](src/year2019/day17.rs) | 425 |
 | 18 | [Many-Worlds Interpretation](https://adventofcode.com/2019/day/18) | [Source](src/year2019/day18.rs) | 1077 |
+| 19 | [Tractor Beam](https://adventofcode.com/2019/day/19) | [Source](src/year2019/day19.rs) | 817 |
 
 ## 2015
 

benches/benchmark.rs

@@ -67,6 +67,7 @@ mod year2019 {
     benchmark!(year2019, day16);
     benchmark!(year2019, day17);
     benchmark!(year2019, day18);
+    benchmark!(year2019, day19);
 }
 
 mod year2020 {

input/year2019/day19.txt

@@ -0,0 +1 @@
+109,424,203,1,21102,11,1,0,1105,1,282,21102,1,18,0,1105,1,259,1201,1,0,221,203,1,21101,0,31,0,1105,1,282,21102,38,1,0,1106,0,259,21001,23,0,2,22101,0,1,3,21101,0,1,1,21102,1,57,0,1105,1,303,2101,0,1,222,21001,221,0,3,20102,1,221,2,21102,259,1,1,21101,80,0,0,1106,0,225,21101,0,111,2,21102,1,91,0,1105,1,303,2102,1,1,223,20101,0,222,4,21102,1,259,3,21102,1,225,2,21102,1,225,1,21101,0,118,0,1105,1,225,20101,0,222,3,21102,148,1,2,21102,1,133,0,1106,0,303,21202,1,-1,1,22001,223,1,1,21102,148,1,0,1106,0,259,2101,0,1,223,20102,1,221,4,21001,222,0,3,21101,0,17,2,1001,132,-2,224,1002,224,2,224,1001,224,3,224,1002,132,-1,132,1,224,132,224,21001,224,1,1,21101,0,195,0,106,0,109,20207,1,223,2,20102,1,23,1,21102,-1,1,3,21101,0,214,0,1105,1,303,22101,1,1,1,204,1,99,0,0,0,0,109,5,2102,1,-4,249,22101,0,-3,1,21202,-2,1,2,21202,-1,1,3,21102,1,250,0,1105,1,225,22102,1,1,-4,109,-5,2106,0,0,109,3,22107,0,-2,-1,21202,-1,2,-1,21201,-1,-1,-1,22202,-1,-2,-2,109,-3,2105,1,0,109,3,21207,-2,0,-1,1206,-1,294,104,0,99,22102,1,-2,-2,109,-3,2106,0,0,109,5,22207,-3,-4,-1,1206,-1,346,22201,-4,-3,-4,21202,-3,-1,-1,22201,-4,-1,2,21202,2,-1,-1,22201,-4,-1,1,21202,-2,1,3,21101,0,343,0,1105,1,303,1105,1,415,22207,-2,-3,-1,1206,-1,387,22201,-3,-2,-3,21202,-2,-1,-1,22201,-3,-1,3,21202,3,-1,-1,22201,-3,-1,2,21201,-4,0,1,21102,384,1,0,1106,0,303,1105,1,415,21202,-4,-1,-4,22201,-4,-3,-4,22202,-3,-2,-2,22202,-2,-4,-4,22202,-3,-2,-3,21202,-4,-1,-2,22201,-3,-2,1,21202,1,1,-4,109,-5,2106,0,0

src/lib.rs

@@ -192,6 +192,7 @@ pub mod year2019 {
     pub mod day16;
     pub mod day17;
     pub mod day18;
+    pub mod day19;
     pub mod intcode;
 }
 

src/main.rs

@@ -105,6 +105,7 @@ fn all_solutions() -> Vec<Solution> {
         solution!(year2019, day16),
         solution!(year2019, day17),
         solution!(year2019, day18),
+        solution!(year2019, day19),
         // 2020
         solution!(year2020, day01),
         solution!(year2020, day02),

src/year2019/day19.rs

@@ -0,0 +1,97 @@
+//! # Tractor Beam
+//!
+//! Finds the approximate boundary of the upper and lower edges of the beam expressed as a slope.
+//! We then skip the relatively expensive intcode test if the x and y coordinates lie outside.
+use super::intcode::*;
+use crate::util::parse::*;
+
+pub struct Input {
+    code: Vec<i64>,
+    lower: i64,
+    upper: i64,
+}
+
+pub fn parse(input: &str) -> Input {
+    let code: Vec<_> = input.iter_signed().collect();
+    let mut lower = 0;
+    let mut upper = 0;
+
+    // Find slope of lower and upper edges, rounding down to prevent false negatives.
+    while !test(&code, lower + 1, 50) {
+        lower += 1;
+    }
+    while !test(&code, 50, upper + 1) {
+        upper += 1;
+    }
+
+    Input { code, lower, upper }
+}
+
+pub fn part1(input: &Input) -> i64 {
+    let code = &input.code;
+    // Handle origin specially
+    let mut result = test(code, 0, 0) as i64;
+
+    // The beam is continuous so we only need to find the left and right edges.
+    for y in 0..50 {
+        let mut left = i64::MAX;
+        let mut right = i64::MIN;
+
+        for x in 0..50 {
+            if precheck(input, x, y) && test(code, x, y) {
+                left = x;
+                break;
+            }
+        }
+        for x in (0..50).rev() {
+            if precheck(input, x, y) && test(code, x, y) {
+                right = x;
+                break;
+            }
+        }
+        if left <= right {
+            result += right - left + 1;
+        }
+    }
+
+    result
+}
+
+pub fn part2(input: &Input) -> i64 {
+    let code = &input.code;
+    let mut x = 0;
+    let mut y = 0;
+    let mut moved = true;
+
+    // Increase the right and bottom edges of our box until they are both inside the beam.
+    while moved {
+        moved = false;
+
+        while !precheck(input, x, y + 99) || !test(code, x, y + 99) {
+            x += 1;
+            moved = true;
+        }
+
+        while !precheck(input, x + 99, y) || !test(code, x + 99, y) {
+            y += 1;
+            moved = true;
+        }
+    }
+
+    10000 * x + y
+}
+
+/// Quick check with some false positives but no false negatives.
+fn precheck(input: &Input, x: i64, y: i64) -> bool {
+    50 * y > input.upper * x && 50 * x > input.lower * y
+}
+
+/// Definitive but slower check.
+fn test(code: &[i64], x: i64, y: i64) -> bool {
+    let mut computer = Computer::new(code);
+    computer.input(x);
+    computer.input(y);
+
+    let State::Output(result) = computer.run() else { unreachable!() };
+    result == 1
+}

tests/test.rs

@@ -60,6 +60,7 @@ mod year2019 {
     mod day16_test;
     mod day17_test;
     mod day18_test;
+    mod day19_test;
 }
 
 mod year2020 {

tests/year2019/day19_test.rs

@@ -0,0 +1,9 @@
+#[test]
+fn part1_test() {
+    // No example data
+}
+
+#[test]
+fn part2_test() {
+    // No example data
+}