Day 15 - task 2

src/days/d15.rs

@@ -1,12 +1,14 @@
 use std::{collections::HashSet, fs};
 
-const ROW: i32 = 2000000;
+const ROW: i32 = 2_000_000;
+const TASK_2_CONST: i32 = 4_000_000;
 
 pub fn solve() {
     let path = "res/15/input.txt";
 
     let contents = fs::read_to_string(path).expect("File read error");
 
+    // parse sensors as tuples with (sensor, beacon, radius)
     let sensors: Vec<((i32, i32), (i32, i32), i32)> = contents
         .lines()
         .filter(|line| *line != "")
@@ -29,10 +31,11 @@ pub fn solve() {
         })
         .collect();
 
+    // task 1
+    // go through sensors, add x-indices to hashset which are covered by sensors on y=2_000_000
     let mut row_map = HashSet::<i32>::new();
-
     sensors.iter().for_each(|sensor| {
-        let ((x1, y1), (x2, y2), rad) = sensor;
+        let ((x1, y1), (_, _), rad) = sensor;
 
         let y_diff = y1.abs_diff(ROW) as i32;
         let x_diff = rad - y_diff;
@@ -44,7 +47,7 @@ pub fn solve() {
             row_map.insert(i);
         })
     });
-
+    // remove all x-indices with beacons
     sensors.iter().for_each(|sensor| {
         let ((_, _), (x2, y2), _) = sensor;
 
@@ -56,47 +59,57 @@ pub fn solve() {
     let res = row_map.len();
     println!("Result 1: {res}");
 
-    let mut sen_tup = Vec::<((i32, i32, i32), (i32, i32, i32))>::new();
-    let mut up_outlines = Vec::<i32>::new();
-    let mut down_outlines = Vec::<i32>::new();
-    sensors.iter().for_each(|s1| {
-        sensors.iter().for_each(|s2| {
-            if s1 != s2 {
-                let ((x1, y1), (_, _), rad1) = *s1;
-                let ((x2, y2), (_, _), rad2) = *s2;
-                let dist = x1.abs_diff(x2) as i32 + y1.abs_diff(y2) as i32;
-                if dist == rad1 + rad2 + 1 {
-                    sen_tup.push(((x1, y1, rad1), (x2, y2, rad2)));
-                    // s2 in quadrant 1
-                    if x1 - x2 < 0 && y1 - y2 > 0 {
-                        down_outlines.push(y1 - (x1 + rad1) - 1)
-                    }
-                    // s2 in quadrant 3
-                    else if x1 - x2 > 0 && y1 - y2 < 0 {
-                        down_outlines.push(y2 - (x2 + rad2) - 1)
-                    }
-                    // s2 in quadrant 2
-                    else if x1 - x2 > 0 && y1 - y2 > 0 {
-                        up_outlines.push(y2 + (x2 + rad2) + 1)
-                    }
-                    // s2 in quadrant 4
-                    else if x1 - x2 < 0 && y1 - y2 < 0 {
-                        up_outlines.push(y1 + (x1 + rad1) + 1)
-                    }
-                }
-            }
-        })
+    // task 2
+    // build vec with all outline points of sensor ranges
+    let mut outline = Vec::<(i32, i32)>::new();
+    sensors.iter().for_each(|sensor| {
+        let ((x, y), (_, _), rad) = *sensor;
+        let mut curr_x = x + rad + 1;
+        let mut curr_y = y;
+        for _ in 0..=rad {
+            curr_x -= 1;
+            curr_y += 1;
+            outline.push((curr_x, curr_y));
+        }
+        for _ in 0..=rad {
+            curr_x -= 1;
+            curr_y -= 1;
+            outline.push((curr_x, curr_y));
+        }
+        for _ in 0..=rad {
+            curr_x += 1;
+            curr_y -= 1;
+            outline.push((curr_x, curr_y));
+        }
+        for _ in 0..=rad {
+            curr_x += 1;
+            curr_y += 1;
+            outline.push((curr_x, curr_y));
+        }
     });
 
-    let mut intersections = Vec::<(i32, i32)>::new();
-    up_outlines.iter().for_each(|up_line| {
-        down_outlines.iter().for_each(|down_line| {
-            if up_line > down_line && up_line % 2 == down_line % 2 {
-                let intersection = down_line + (up_line - down_line) / 2;
-                // TODO continue
+    // find point that is out of RAD for each sensor
+    let mut res_point = (-1, -1);
+    for p in outline {
+        let mut point_in_sensor_range = false;
+        for s in &sensors {
+            let dist = p.0.abs_diff(s.0 .0) as i32 + p.1.abs_diff(s.0 .1) as i32;
+            if dist <= s.2 {
+                point_in_sensor_range = true;
+                break;
             }
-        })
-    });
+        }
+        if !point_in_sensor_range
+            && p.0 >= 0
+            && p.0 <= TASK_2_CONST
+            && p.1 >= 0
+            && p.1 <= TASK_2_CONST
+        {
+            res_point = p;
+            break;
+        }
+    }
 
-    sen_tup.iter().for_each(|tup| {});
+    let res = TASK_2_CONST as i64 * res_point.0 as i64 + res_point.1 as i64;
+    println!("Result 2: {res}");
 }