Year 2017 Day 2

Author: maneatingape

README.md

@@ -242,6 +242,7 @@ pie
 | Day | Problem | Solution | Benchmark (μs) |
 | --- | --- | --- | --: |
 | 1 | [Inverse Captcha](https://adventofcode.com/2017/day/1) | [Source](src/year2017/day01.rs) | 1 |
+| 2 | [Corruption Checksum](https://adventofcode.com/2017/day/2) | [Source](src/year2017/day02.rs) | 3 |
 
 ## 2016
 

benches/benchmark.rs

@@ -93,6 +93,7 @@ mod year2016 {
 
 mod year2017 {
     benchmark!(year2017, day01);
+    benchmark!(year2017, day02);
 }
 
 mod year2019 {

input/year2017/day02.txt

@@ -0,0 +1,16 @@
+1208	412	743	57	1097	53	71	1029	719	133	258	69	1104	373	367	365
+4011	4316	1755	4992	228	240	3333	208	247	3319	4555	717	1483	4608	1387	3542
+675	134	106	115	204	437	1035	1142	195	1115	569	140	1133	190	701	1016
+4455	2184	5109	221	3794	246	5214	4572	3571	3395	2054	5050	216	878	237	3880
+4185	5959	292	2293	118	5603	2167	5436	3079	167	243	256	5382	207	5258	4234
+94	402	126	1293	801	1604	1481	1292	1428	1051	345	1510	1417	684	133	119
+120	1921	115	3188	82	334	366	3467	103	863	3060	2123	3429	1974	557	3090
+53	446	994	71	872	898	89	982	957	789	1040	100	133	82	84	791
+2297	733	575	2896	1470	169	2925	1901	195	2757	1627	1216	148	3037	392	221
+1343	483	67	1655	57	71	1562	447	58	1561	889	1741	1338	88	1363	560
+2387	3991	3394	6300	2281	6976	234	204	6244	854	1564	210	195	7007	3773	3623
+1523	77	1236	1277	112	171	70	1198	86	1664	1767	75	315	143	1450	1610
+168	2683	1480	200	1666	1999	3418	2177	156	430	2959	3264	2989	136	110	3526
+8702	6973	203	4401	8135	7752	1704	8890	182	9315	255	229	6539	647	6431	6178
+2290	157	2759	3771	4112	2063	153	3538	3740	130	3474	1013	180	2164	170	189
+525	1263	146	954	188	232	1019	918	268	172	1196	1091	1128	234	650	420

src/lib.rs

@@ -221,6 +221,7 @@ pub mod year2016 {
 /// # A technical support callout from the Elves escalates rapidly.
 pub mod year2017 {
     pub mod day01;
+    pub mod day02;
 }
 
 /// # Rescue Santa from deep space with a solar system adventure.

src/main.rs

@@ -141,7 +141,7 @@ fn year2016() -> Vec<Solution> {
 }
 
 fn year2017() -> Vec<Solution> {
-    vec![solution!(year2017, day01)]
+    vec![solution!(year2017, day01), solution!(year2017, day02)]
 }
 
 fn year2019() -> Vec<Solution> {

src/year2017/day02.rs

@@ -0,0 +1,39 @@
+//! # Corruption Checksum
+//!
+//! Part two is `O(n²)` complexity but at least we can reduce by a factor of two by sorting
+//! each line first, allowing us to only compare each number against those that are greater.
+//! As a minor benefit this makes part one faster too.
+use crate::util::parse::*;
+
+type Input = Vec<Vec<u32>>;
+
+pub fn parse(input: &str) -> Input {
+    input
+        .lines()
+        .map(|line| {
+            let mut values: Vec<_> = line.iter_unsigned().collect();
+            values.sort_unstable();
+            values
+        })
+        .collect()
+}
+
+pub fn part1(input: &Input) -> u32 {
+    input.iter().map(|values| values[values.len() - 1] - values[0]).sum()
+}
+
+pub fn part2(input: &Input) -> u32 {
+    input
+        .iter()
+        .map(|values| {
+            for i in 0..values.len() {
+                for j in i + 1..values.len() {
+                    if values[j] % values[i] == 0 {
+                        return values[j] / values[i];
+                    }
+                }
+            }
+            unreachable!()
+        })
+        .sum()
+}

tests/test.rs

@@ -86,6 +86,7 @@ mod year2016 {
 
 mod year2017 {
     mod day01_test;
+    mod day02_test;
 }
 
 mod year2019 {

tests/year2017/day02_test.rs

@@ -0,0 +1,23 @@
+use aoc::year2017::day02::*;
+
+const FIRST_EXAMPLE: &str = "\
+5 1 9 5
+7 5 3
+2 4 6 8";
+
+const SECOND_EXAMPLE: &str = "\
+5 9 2 8
+9 4 7 3
+3 8 6 5";
+
+#[test]
+fn part1_test() {
+    let input = parse(FIRST_EXAMPLE);
+    assert_eq!(part1(&input), 18);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(SECOND_EXAMPLE);
+    assert_eq!(part2(&input), 9);
+}