Day 2

Cargo.lock

@@ -1,7 +1,25 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
+
+[[package]]
+name = "either"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "60b1af1c220855b6ceac025d3f6ecdd2b7c4894bfe9cd9bda4fbb4bc7c0d4cf0"
+
+[[package]]
+name = "itertools"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "413ee7dfc52ee1a4949ceeb7dbc8a33f2d6c088194d9f922fb8318faf1f01186"
+dependencies = [
+ "either",
+]
 
 [[package]]
 name = "testing"
 version = "0.1.0"
+dependencies = [
+ "itertools",
+]

Cargo.toml

@@ -11,3 +11,4 @@ pedantic = "warn"
 all = "warn"
 
 [dependencies]
+itertools = "0.13.0"

src/main.rs

@@ -1,16 +1,24 @@
 use std::{
-    collections::HashMap,
     fs::File,
-    io::{BufRead, BufReader},
+    io::{BufRead as _, BufReader},
 };
 
+fn get_lines(name: &str) -> impl Iterator<Item = String> {
+    BufReader::new(File::open(name).unwrap())
+        .lines()
+        .map(|line| line.unwrap())
+}
+
+mod day1 {
+    use std::collections::HashMap;
+
+    use crate::get_lines;
+
     #[allow(dead_code)]
-fn day1_1() {
-    let reader = BufReader::new(File::open("input.txt").unwrap());
+    pub fn task1() {
         let mut a = Vec::<i32>::new();
         let mut b = Vec::<i32>::new();
-    for line in reader.lines() {
-        let line = line.unwrap();
+        for line in get_lines("input.txt") {
             let (a1, b1) = line.trim_end().split_once("   ").unwrap();
             a.push(a1.parse().unwrap());
             b.push(b1.parse().unwrap());
@@ -22,12 +30,10 @@ fn day1_1() {
     }
 
     #[allow(dead_code)]
-fn day1_2() {
-    let reader = BufReader::new(File::open("input.txt").unwrap());
+    pub fn task2() {
         let mut a = Vec::<u32>::new();
         let mut b = HashMap::<u32, u32>::new();
-    for line in reader.lines() {
-        let line = line.unwrap();
+        for line in get_lines("input.txt") {
             let (a1, b1) = line.trim_end().split_once("   ").unwrap();
             a.push(a1.parse().unwrap());
             *b.entry(b1.parse().unwrap()).or_insert(0) += 1;
@@ -35,8 +41,69 @@ fn day1_2() {
         let result: u32 = a.into_iter().map(|a| a * *b.get(&a).unwrap_or(&0)).sum();
         println!("{result}");
     }
+}
+
+mod day2 {
+    use itertools::Itertools;
+
+    use crate::get_lines;
+
+    fn safe(iter: impl Iterator<Item = i32>) -> bool {
+        let mut order = None;
+        for (a, b) in iter.tuple_windows() {
+            if !(1..4).contains(&(a - b).abs()) {
+                return false;
+            }
+            if order.is_none() {
+                order = Some(a.cmp(&b));
+            } else if order != Some(a.cmp(&b)) {
+                return false;
+            }
+        }
+        true
+    }
+
+    fn parse_line(line: &str) -> impl Iterator<Item = i32> + '_ {
+        line.trim()
+            .split(' ')
+            .map(|num| num.parse::<i32>().unwrap())
+    }
+
+    #[allow(dead_code)]
+    pub fn task1() {
+        let result = get_lines("input.txt")
+            .filter(|line| safe(parse_line(line)))
+            .count();
+        println!("{result}");
+    }
+
+    #[allow(dead_code)]
+    pub fn task2() {
+        let result = get_lines("input.txt")
+            .filter(|line| {
+                let numbers = parse_line(line).collect_vec();
+                if safe(numbers.iter().copied()) {
+                    return true;
+                }
+                let mut test = Vec::with_capacity(numbers.len() - 1);
+                for i in 0..numbers.len() {
+                    test.extend_from_slice(&numbers[..i]);
+                    test.extend_from_slice(&numbers[i + 1..]);
+                    if safe(test.iter().copied()) {
+                        return true;
+                    }
+                    test.clear();
+                }
+                false
+            })
+            .count();
+        println!("{result}");
+    }
+}
 
 fn main() {
-    day1_1();
-    day1_2();
+    // day1::task1();
+    // day1::task1();
+    day2::task1();
+    day2::task2();
 }