01

day_01/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day_01"
+version = "0.1.0"

day_01/Cargo.toml

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+[package]
+name = "day_01"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

day_01/example.txt

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+3   4
+4   3
+2   5
+1   3
+3   9
+3   3

day_01/src/main.rs

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+use std::{collections::HashMap, fs::read_to_string};
+
+fn main() {
+    part_01();
+    part_02();
+}
+
+fn part_02() {
+    let mut left = vec![];
+    let mut right = HashMap::new();
+
+    read_to_string("input.txt")
+        .unwrap()
+        .lines()
+        .for_each(|line| {
+            let mut iter = line.split_whitespace();
+            left.push(iter.next().unwrap().parse::<isize>().unwrap());
+            right
+                .entry(iter.next().unwrap().parse::<isize>().unwrap())
+                .and_modify(|e| *e += 1)
+                .or_insert(1);
+        });
+
+    let mut sum = 0;
+    for number in left {
+        sum += number * *right.entry(number).or_default();
+    }
+    println!("{sum}");
+}
+
+fn part_01() {
+    let mut left = vec![];
+    let mut right = vec![];
+    read_to_string("input.txt")
+        .unwrap()
+        .lines()
+        .for_each(|line| {
+            let mut iter = line.split_whitespace();
+            left.push(iter.next().unwrap().parse::<isize>().unwrap());
+            right.push(iter.next().unwrap().parse::<isize>().unwrap());
+        });
+
+    left.sort_unstable();
+    right.sort_unstable();
+
+    let mut sum = 0;
+
+    for (l, r) in left.into_iter().zip(right) {
+        sum += (l - r).abs();
+    }
+    println!("{sum}");
+}