day11: rust

11/day11.rs

@@ -0,0 +1,74 @@
+use std::io::{self, BufRead};
+
+const ADD_TO_EMPTY1: usize = 1;
+const ADD_TO_EMPTY2: usize = 1_000_000-1;
+fn add_empty_columns(galaxy_positions: &mut Vec<(usize, usize)>, add_to_empty: usize) {
+    let mut last_x: usize = galaxy_positions[0].0;
+    let mut empty_columns: usize = 0;
+    for i in 1..galaxy_positions.len() {
+        if galaxy_positions[i].0 > last_x + 1 {
+            empty_columns += (galaxy_positions[i].0 - last_x - 1) * add_to_empty;
+        }
+        last_x = galaxy_positions[i].0;
+        galaxy_positions[i].0 += empty_columns;
+    }
+}
+
+fn get_distance_sum(galaxy_positions: &Vec<(usize, usize)>) -> usize {
+    let mut distance_sum: usize = 0;
+    for i in 0..galaxy_positions.len() - 1 {
+        for j in i+1..galaxy_positions.len() {
+            // println!("{}<->{}: {}", i, j, galaxy_positions[i].0.abs_diff(galaxy_positions[j].0) + galaxy_positions[i].1.abs_diff(galaxy_positions[j].1));
+            distance_sum += galaxy_positions[i].0.abs_diff(galaxy_positions[j].0);
+            distance_sum += galaxy_positions[i].1.abs_diff(galaxy_positions[j].1);
+        }
+    }
+    return distance_sum;
+}
+
+fn main() {
+    // let input = "example.txt";
+    let input = "input.txt";
+    let lines = read_lines(&input);
+    let mut galaxy_positions1: Vec<(usize, usize)> = Vec::new();
+    let mut galaxy_positions2: Vec<(usize, usize)> = Vec::new();
+    galaxy_positions1.reserve(300);
+    galaxy_positions2.reserve(300);
+    let mut y1: usize = 0;
+    let mut y2: usize = 0;
+    for line in lines.map(|r| r.ok().unwrap()) {
+        let mut galaxies = line.chars().enumerate().filter(|(_, c)| *c == '#');
+        if let Some((x, _)) = galaxies.next() {
+            galaxy_positions1.push((x, y1));
+            galaxy_positions2.push((x, y2));
+            while let Some((x, _)) = galaxies.next() {
+                galaxy_positions1.push((x, y1));
+                galaxy_positions2.push((x, y2));
+            }
+        }
+        else {  // empty lines are double the size
+            y1 += ADD_TO_EMPTY1;
+            y2 += ADD_TO_EMPTY2;
+        }
+        y1 += 1;
+        y2 += 1;
+    }
+    // sort by x
+    galaxy_positions1.sort_unstable_by(|a ,b| a.0.cmp(&b.0));
+    galaxy_positions2.sort_unstable_by(|a ,b| a.0.cmp(&b.0));
+    add_empty_columns(&mut galaxy_positions1, ADD_TO_EMPTY1);
+    add_empty_columns(&mut galaxy_positions2, ADD_TO_EMPTY2);
+    let distance_sum1: usize = get_distance_sum(&galaxy_positions1);
+    println!("Sum of galaxy distances: (1): {}", distance_sum1);
+    let distance_sum2: usize = get_distance_sum(&galaxy_positions2);
+    println!("Sum of galaxy distances: (2): {}", distance_sum2);
+}
+
+
+fn read_lines<P>(filename: P) -> io::Lines<io::BufReader<std::fs::File>>
+where P: AsRef<std::path::Path>, {
+    return match std::fs::File::open(filename) {
+        Err(why) => panic!("Could not open file. {}", why),
+        Ok(file) => std::io::BufReader::new(file).lines()
+    };
+}