Day one

.gitignore

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+input/
+.idea

day-01-rust/.gitignore

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+target/

day-01-rust/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day-01-rust"
+version = "0.1.0"

day-01-rust/Cargo.toml

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+[package]
+name = "day-01-rust"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

day-01-rust/src/main.rs

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+mod task1;
+mod task2;
+
+fn main() {
+    let args = std::env::args().collect::<Vec<_>>();
+    if args.len() != 3 {
+        println!("Usage: {} <1|2> <input file>", args[0]);
+        return;
+    }
+    let task = args.get(1).unwrap();
+    match task.as_str() {
+        "1" => {
+            task1::run(&*read_input(args.get(2).unwrap()));
+        }
+        "2" => {
+            task2::run(&*read_input(args.get(2).unwrap()));
+        }
+        _ => { eprintln!("First argument has to be 1 or 2") }
+    }
+}
+
+fn read_input(file: &str) -> String {
+    std::fs::read_to_string(file).expect("Could not read file")
+}

day-01-rust/src/task1.rs

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+use std::str::FromStr;
+
+pub fn run(input: &str) {
+    let mut first = Vec::<i64>::new();
+    let mut second = Vec::<i64>::new();
+    for line in input.split('\n') {
+        if let Some((first_part, second_part)) = line.split_once("   ") {
+            match i64::from_str(first_part) {
+                Ok(n) => first.push(n),
+                Err(err) => {
+                    eprintln!("Failed to parse first number from {}: {}", first_part, err);
+                }
+            }
+            match i64::from_str(second_part) {
+                Ok(n) => second.push(n),
+                Err(err) => {
+                    eprintln!("Failed to parse second number from {}: {}", second_part, err);
+                }
+            }
+        }
+    }
+
+    first.sort();
+    second.sort();
+    let sum = first.iter().zip(second.iter()).map(|(a, b)| a.abs_diff(*b)).sum::<u64>();
+    println!("Total difference: {}", sum);
+}

day-01-rust/src/task2.rs

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+use std::collections::HashMap;
+use std::str::FromStr;
+
+pub fn run(input: &str) {
+    let mut first = Vec::<i64>::new();
+    let mut second = Vec::<i64>::new();
+    for line in input.split('\n') {
+        if let Some((first_part, second_part)) = line.split_once("   ") {
+            match i64::from_str(first_part) {
+                Ok(n) => first.push(n),
+                Err(err) => {
+                    eprintln!("Failed to parse first number from {}: {}", first_part, err);
+                }
+            }
+            match i64::from_str(second_part) {
+                Ok(n) => second.push(n),
+                Err(err) => {
+                    eprintln!("Failed to parse second number from {}: {}", second_part, err);
+                }
+            }
+        }
+    }
+
+    let mut second_counts = HashMap::<i64, i64>::new();
+    for element in second {
+        *second_counts.entry(element).or_insert(0) += 1;
+    }
+    
+    let result = first.iter().map(|num| num * second_counts.get(num).unwrap_or(&0)).sum::<i64>();
+    println!("Similarity: {}", result);
+}