Day 7

1 files changed, 28 insertions, 0 deletions

diff --git a/day7/src/main.rs b/day7/src/main.rs
new file mode 100644
index 0000000..8a44c07
--- /dev/null
+++ b/day7/src/main.rs
@@ -0,0 +1,28 @@
+use std::fs;
+use std::path::Path;
+
+/* AOC21 Day 7: https://adventofcode.com/2021/day/7
+ *
+ * Some details about the solutions can be found here:
+ *
+ *  https://web.archive.org/web/20211208180308/https://cdn.discordapp.com/attachments/541932275068174359/917882191298592788/crab_submarines.pdf
+ *
+ */
+fn main() {
+    let input = Path::new("resources").join("input.txt");
+    let content = fs::read_to_string(input).expect("Unable to read input file");
+    let mut report: Vec<i32> = content.split(",").map(|x| x.parse().expect("Malformed input")).collect();
+    report.sort();
+    println!("Ex1: The result is {}", ex1(&report));
+    println!("Ex1: The result is {}", ex2(&report));
+}
+
+fn ex1(report: &[i32]) -> i32 {
+    let median = report[(report.len() as f32 / 2.).round() as usize];
+    report.iter().fold(0, |a,x| a + (x-median).abs())
+}
+
+fn ex2(report: &[i32]) -> i32 {
+    let mean = (report.iter().sum::<i32>() as f32 / report.len() as f32).floor() as i32;
+    report.iter().fold(0, |a,x| { let d = (x-mean).abs(); a + (d*(d+1)/2) })
+}