Day 4

src/day1.rs

@@ -1,6 +1,7 @@
 pub fn day1() {
-    let puzzle_input = std::fs::read_to_string("res/puzzle_1.txt").unwrap();
-    let (mut left, mut right): (Vec<u64>, Vec<u64>) = puzzle_input
+    let input = crate::input(1);
+
+    let (mut left, mut right): (Vec<u64>, Vec<u64>) = input
         .lines()
         .filter(|line| !line.is_empty())
         .map(|line| {

src/day2.rs

@@ -1,9 +1,9 @@
 const DAMPENING: bool = true;
 
 pub fn day2() {
-    let puzzle_input = std::fs::read_to_string("res/puzzle_2.txt").unwrap();
+    let input = crate::input(2);
 
-    let lines: Vec<Vec<u64>> = puzzle_input
+    let lines: Vec<Vec<u64>> = input
         .lines()
         .filter(|line| !line.is_empty())
         .map(|line| {

src/day3.rs

@@ -1,14 +1,13 @@
-use std::fs;
 use regex::Regex;
 
 const READ_ALL: bool = false;
 
 pub fn day3() {
-    let input_text = fs::read_to_string("res/puzzle_3.txt").unwrap();
+    let input = crate::input(3);
 
     let mut total: u64 = 0;
     let mut enabled = true;
-    for statement in Regex::new(r"(?:mul\((?<a>\d{1,3}),(?<b>\d{1,3})\))|(?<do>do\(\))|(?<dont>don't\(\))").unwrap().captures_iter(&input_text) {
+    for statement in Regex::new(r"(?:mul\((?<a>\d{1,3}),(?<b>\d{1,3})\))|(?<do>do\(\))|(?<dont>don't\(\))").unwrap().captures_iter(&input) {
         if statement.name("do").is_some() {
             enabled = true;
         } else if statement.name("dont").is_some() {

src/day4.rs

@@ -0,0 +1,53 @@
+const DIRECTIONS: [(i64, i64); 8] = [
+    (1, 0),
+    (-1, 0),
+    (0, 1),
+    (0, -1),
+    (1, 1),
+    (-1, -1),
+    (1, -1),
+    (-1, 1),
+];
+
+pub fn day4() {
+    let input = crate::input(4);
+    let grid: Vec<Vec<char>> = input.lines().map(|line| line.chars().collect()).collect();
+
+    let mut total: usize = 0;
+    for y in 0..grid.len() {
+        for x in 0..grid[y].len() {
+            total += DIRECTIONS
+                .iter()
+                .filter(|(dx, dy)| check_word("XMAS", &grid, x, y, *dx, *dy))
+                .count();
+        }
+    }
+
+    println!("Total: {}", total);
+
+    let mut total_crossed: usize = 0;
+    for y in 1..(grid.len() - 1) {
+        for x in 1..(grid[y].len() - 1) {
+            let a = check_word("MAS", &grid, x - 1, y - 1, 1, 1)
+                || check_word("MAS", &grid, x + 1, y + 1, -1, -1);
+            let b = check_word("MAS", &grid, x - 1, y + 1, 1, -1)
+                || check_word("MAS", &grid, x + 1, y - 1, -1, 1);
+            if a && b {
+                total_crossed += 1;
+            }
+        }
+    }
+
+    println!("Total Crossed: {}", total_crossed);
+}
+
+fn check_word(word: &str, grid: &Vec<Vec<char>>, x: usize, y: usize, dx: i64, dy: i64) -> bool {
+    for d in 0..word.len() {
+        let a = (x as i64 + (d as i64 * dx)) as usize;
+        let b = (y as i64 + (d as i64 * dy)) as usize;
+        if grid.get(b).map(|it| it.get(a).copied()) != Some(word.chars().nth(d)) {
+            return false;
+        }
+    }
+    true
+}

src/main.rs

@@ -1,7 +1,21 @@
 mod day1;
 mod day2;
 mod day3;
+mod day4;
 
 fn main() {
-    day3::day3();
+    day4::day4();
+}
+
+pub fn input(day: u8) -> String {
+    dotenvy::dotenv().ok();
+    let token = std::env::var("AOC_TOKEN").expect("AOC_TOKEN must be set in .env file");
+
+    let client = reqwest::blocking::Client::new();
+    client.get(format!("https://adventofcode.com/2024/day/{}/input", day))
+        .header("cookie", format!("session={}", token))
+        .send()
+        .expect("Failed to get input")
+        .text()
+        .expect("Failed to read response text")
 }