day03 task 2

src/tasks/day03.rs

@@ -1,5 +1,6 @@
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::fs;
+use std::iter;
 
 #[allow(dead_code)]
 pub fn run() {
@@ -7,6 +8,7 @@ pub fn run() {
     let p1: Vec<&str> = content.lines().next().unwrap().split(",").collect();
     let p2: Vec<&str> = content.lines().skip(1).next().unwrap().split(",").collect();
     task1(&p1, &p2);
+    task2(&p1, &p2);
 }
 
 fn task1(p1: &Vec<&str>, p2: &Vec<&str>) {
@@ -17,7 +19,7 @@ fn task1(p1: &Vec<&str>, p2: &Vec<&str>) {
         .min_by_key(|(a, b)| a.abs() + b.abs())
         .unwrap();
     println!(
-        "Closest point is at distance {}",
+        "Task 1: Closest point is at distance {}",
         closest_distance.0.abs() + closest_distance.1.abs()
     );
 }
@@ -73,3 +75,56 @@ fn visited_points(p: &Vec<&str>) -> HashSet<(i32, i32)> {
         .flatten()
         .collect()
 }
+
+fn task2(p1: &Vec<&str>, p2: &Vec<&str>) {
+    let points1 = get_points(&p1);
+    let points2 = get_points(&p2);
+    let set1 = points1
+        .keys()
+        .map(|(x, y)| (*x, *y))
+        .collect::<HashSet<(i32, i32)>>();
+    let set2 = points2
+        .keys()
+        .map(|(x, y)| (*x, *y))
+        .collect::<HashSet<(i32, i32)>>();
+    let p = set1
+        .intersection(&set2)
+        .min_by_key(|p| points1[p] + points2[p])
+        .unwrap();
+    println!(
+        "Task 2: shortest is at {:?} with distances {}/{} = {}",
+        p,
+        points1[p],
+        points2[p],
+        points1[p] + points2[p]
+    );
+    // 20384 is too short
+}
+
+fn get_points(path: &Vec<&str>) -> HashMap<(i32, i32), usize> {
+    let mut directions = HashMap::new();
+    directions.insert('U', (0, 1));
+    directions.insert('D', (0, -1));
+    directions.insert('L', (-1, 0));
+    directions.insert('R', (1, 0));
+    path.iter()
+        .map(|it| {
+            let direction = it.chars().next().unwrap();
+            let number = it[1..].parse::<usize>().unwrap();
+            iter::repeat(direction).take(number)
+        })
+        .flatten()
+        .scan((0, 0), |(sx, sy), dir| {
+            let (dx, dy) = directions[&dir];
+            *sx += dx;
+            *sy += dy;
+            Some((*sx, *sy))
+        })
+        .enumerate()
+        .fold(HashMap::new(), |mut hm, (i, point)| {
+            if !hm.contains_key(&point) {
+                hm.insert(point, i + 1);
+            }
+            hm
+        })
+}