day03 task 1 'nicer' version

src/tasks/day03.rs

@@ -0,0 +1,65 @@
+use std::collections::HashSet;
+use std::fs;
+
+#[allow(dead_code)]
+pub fn run() {
+    let content = fs::read_to_string("input/day03.txt").unwrap();
+    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);
+}
+
+fn task1(p1: &Vec<&str>, p2: &Vec<&str>) {
+    let points1 = visited_points(&p1);
+    let points2 = visited_points(&p2);
+    let closest_distance = points1
+        .intersection(&points2)
+        .min_by_key(|(a, b)| a.abs() + b.abs())
+        .unwrap();
+    println!(
+        "Closest point is at distance {}",
+        closest_distance.0.abs() + closest_distance.1.abs()
+    );
+}
+
+/**
+ * returns all visited points, the origin is left out, unless it is visited once again
+ */
+fn visited_points(p: &Vec<&str>) -> HashSet<(i32, i32)> {
+    p.iter()
+        .map(|step| {
+            let direction = step.chars().next().unwrap();
+            let number = step[1..].parse::<i32>().unwrap();
+            (direction, number)
+        })
+        .scan((0, 0), |(cx, cy), (direction, number)| {
+            let sx = *cx;
+            let sy = *cy;
+            let mut tx = *cx;
+            let mut ty = *cy;
+            let iter: Box<dyn Iterator<Item = (i32, i32)>> = match direction {
+                'U' => {
+                    ty += number;
+                    Box::new((*cy + 1..=ty).map(move |y| (sx, y)))
+                }
+                'D' => {
+                    ty -= number;
+                    Box::new((ty..*cy).map(move |y| (sx, y)))
+                }
+                'R' => {
+                    tx += number;
+                    Box::new((*cx + 1..=tx).map(move |x| (x, sy)))
+                }
+                'L' => {
+                    tx -= number;
+                    Box::new((tx..*cx).map(move |x| (x, sy)))
+                }
+                _ => panic!("unknown direction {}", direction),
+            };
+            *cx = tx;
+            *cy = ty;
+            Some(iter)
+        })
+        .flatten()
+        .collect()
+}