Add day1

2024/day1/.gitignore

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+/target
+input.txt

2024/day1/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day1"
+version = "0.1.0"

2024/day1/Cargo.toml

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+[package]
+name = "day1"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

2024/day1/src/main.rs

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+use std::fs;
+
+fn main() {
+    let input = fs::read_to_string("./input.txt").unwrap();
+    let mut column1 = Vec::new();
+    let mut column2 = Vec::new();
+    for line in input.lines() {
+        let mut split = line.split_whitespace();
+        column1.push(split.next().unwrap().parse::<i32>().unwrap());
+        column2.push(split.next().unwrap().parse::<i32>().unwrap());
+    }
+    column1.sort_unstable();
+    column2.sort_unstable();
+
+    println!("Solution 1: {}", puzzle1(&column1, &column2));
+    println!("Solution 2: {}", puzzle2(&column1, &column2));
+}
+
+fn puzzle1(column1: &[i32], column2: &[i32]) -> i32 {
+    column1
+        .iter()
+        .zip(column2)
+        .map(|(c1, c2)| (c1 - c2).abs())
+        .sum()
+}
+
+fn puzzle2(column1: &[i32], column2: &[i32]) -> i32 {
+    column1
+        .iter()
+        .map(|c1| column2.iter().filter(|&c2| c1 == c2).count() as i32 * c1)
+        .sum()
+}