feat: added day 1 part 1 and 2

Signed-off-by: Louis Vallat <contact@louis-vallat.fr>

.gitea/workflows/build_and_run.yml

@@ -0,0 +1,22 @@
+name: Build and run challenges
+defaults:
+  run:
+    shell: sh
+on:
+  push:
+
+
+jobs:
+  build-and-run:
+    name: Challenge for day
+    strategy:
+      matrix:
+        day_number: [1]
+    runs-on: rust-bookworm
+    steps:
+      - name: Check out repository code
+        uses: actions/checkout@v4
+      - name: Run challenge
+        run: |
+          cd day${{ matrix.day_number }}
+          cargo run --release ./input

.gitignore

@@ -0,0 +1,3 @@
+target
+Cargo.lock
+.idea/

day1/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day-1"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day1/src/main.rs

@@ -0,0 +1,59 @@
+use std::collections::HashMap;
+use std::{env, fs};
+
+fn read_input(path: &str) -> String {
+    fs::read_to_string(path).expect("Cannot read file.")
+}
+
+fn parse_input(input: &str) -> (Vec<i32>, Vec<i32>) {
+    let (mut right, mut left) =
+        input
+            .lines()
+            .filter(|line| !line.is_empty())
+            .fold((vec![], vec![]), |mut acc, line| {
+                let split = line.trim().split_once("   ").expect("Cannot split line.");
+                acc.0.push(
+                    split
+                        .0
+                        .parse::<i32>()
+                        .expect("Cannot parse integer on the left."),
+                );
+                acc.1.push(
+                    split
+                        .1
+                        .parse::<i32>()
+                        .expect("Cannot parse integer on the right."),
+                );
+                acc
+            });
+    right.sort();
+    left.sort();
+    (left, right)
+}
+
+fn part_1(left: &Vec<i32>, right: &Vec<i32>) -> i32 {
+    left.iter()
+        .enumerate()
+        .map(|(i, x)| (x - right[i]).abs())
+        .sum()
+}
+
+fn part_2(left: &Vec<i32>, right: &Vec<i32>) -> i32 {
+    let mut occur = HashMap::new();
+    for x in right.iter() {
+        *occur.entry(x).or_insert(0) += 1;
+    }
+
+    left.iter().map(|x| x * occur.get(x).unwrap_or(&0)).sum()
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        let input = read_input(&arg);
+        let (left, right) = parse_input(&input);
+        println!("[{}]", &arg);
+        println!("\t[Part 1] => Answer is '{}'.", part_1(&left, &right));
+        println!("\t[Part 2] => Answer is '{}'.", part_2(&left, &right));
+    }
+}