aoc_2024_day1_rust

use std::collections::HashMap;
use std::fs::File;
use std::io::{BufRead, BufReader};
use std::time::Instant;

fn create_sorted_vectors_from_file(
    file_name: &str,
) -> Result<(Vec<i32>, Vec<i32>), std::io::Error> {
    let file = File::open(file_name)?;
    let reader = BufReader::new(file);

    let mut col1 = Vec::new();
    let mut col2 = Vec::new();

    for line in reader.lines() {
        let line = line?;
        let numbers: Vec<i32> = line
            .split_whitespace()
            .map(|s| s.parse().unwrap())
            .collect();

        if numbers.len() == 2 {
            col1.push(numbers[0]);
            col2.push(numbers[1]);
        }
    }

    col1.sort();
    col2.sort();

    Ok((col1, col2))
}

fn calculate_l1_distance(vec1: &[i32], vec2: &[i32]) -> i64 {
    vec1.iter()
        .zip(vec2.iter())
        .map(|(a, b)| (a - b).abs() as i64)
        .sum()
}

fn find_similarity_score(vec1: &[i32], vec2: &[i32]) -> i64 {
    let mut vec2_counter: HashMap<i32, u32> = HashMap::new();
    for &el in vec2 {
        *vec2_counter.entry(el).or_insert(0) += 1;
    }
    let mut score = 0i64;
    for el in vec1 {
        if let Some(&count) = vec2_counter.get(el) {
            score += (el.clone() as i64) * (count as i64)
        }
    }
    score
}
fn main() {
    let start = Instant::now();
    match create_sorted_vectors_from_file("input.txt") {
        Ok((col1, col2)) => {
            if col1.len() == col2.len() {
                let l1_distance = calculate_l1_distance(&col1, &col2);
                let similarity_score = find_similarity_score(&col1, &col2);
                println!("L1 distance between the two vectors: {}", l1_distance);
                println!(
                    "similarity score between the two vectors: {}",
                    similarity_score
                );
            } else {
                println!("Error: Vectors have different lengths");
            }
        }
        Err(e) => println!("Error reading file: {}", e),
    }
    let duration = start.elapsed();
    println!("Time elapsed: {:?}", duration);
}