day9 part 2 :)

src/day9.rs

@@ -1,13 +1,16 @@
+use itertools::Itertools;
+
 #[aoc(day9, part1)]
 pub fn part1(input: &str) -> i64 {
     let mut coords = parse(input);
     coords.sort_unstable_by_key(|x| x.0 + x.1);
-    //println!("{:?}", coords);
     let mut area = 0;
     for (x1, y1) in coords.iter().rev().take(10) {
         for (x2, y2) in coords.iter().take(10) {
+            if ((x1 - x2 + 1) * (y1 - y2 + 1)) > area {
+                println!("{:?}", ((x1, y1), (x2, y2)))
+            };
             area = area.max((x1 - x2 + 1) * (y1 - y2 + 1));
-            //println!("{}", area);
         }
     }
     area
@@ -15,69 +18,66 @@ pub fn part1(input: &str) -> i64 {
 
 #[aoc(day9, part2)]
 pub fn part2(input: &str) -> i64 {
-    let mut coords = parse(input);
-    let (x_lines, y_lines) = rg_lines(&coords);
-    coords.sort_unstable_by_key(|x| x.0 + x.1);
-
-    println!("{:?}", coords);
-    println!("{:?}", x_lines);
-    println!("{:?}", y_lines);
-
+    let coords = parse(input);
     let mut area = 0;
-    for (x1, y1) in coords.iter() {
-        for (x2, y2) in coords.iter() {
-            if y_lines
-                .iter()
-                .filter(|(x, y_a, y_b)| x2 == x && y_a <= y1 && y1 <= y_b)
-                .count()
-                > 1
-            // && x_lines
-            //     .iter()
-            //     .filter(|(x, y_a, y_b)| x1 == x && y_a <= y2 && y2 <= y_b)
-            //     .count()
-            //     > 1
-            // && y_lines
-            //     .iter()
-            //     .filter(|(y, x_a, x_b)| y1 == y && x_a <= x2 && x2 <= x_b)
-            //     .count()
-            //     > 1
-            // && x_lines
-            //     .iter()
-            //     .filter(|(y, x_a, x_b)| y2 == y && x_a <= x1 && x1 <= x_b)
-            //     .count()
-            //     > 1
-            {
-                println!("check");
-                area = area.max((x1 - x2 + 1) * (y1 - y2 + 1));
+    for i1 in 0..coords.len() {
+        for i3 in (0)..coords.len() {
+            let this_area = ((coords[i1].0 - coords[i3].0).abs() + 1)
+                * ((coords[i1].1 - coords[i3].1).abs() + 1);
+
+            if this_area > area && check(i1, i3, &coords) {
+                area = this_area;
             }
         }
     }
     area
 }
 
-fn rg_lines(coords: &Vec<(i64, i64)>) -> (Vec<(i64, i64, i64)>, Vec<(i64, i64, i64)>) {
-    let x_lines = coords
-        .iter()
-        .map(|(x1, y1)| {
-            coords
-                .iter()
-                .filter(move |(x2, y2)| x1 == x2 && y1 < y2)
-                .map(move |(x2, y2)| (*x1, *y1, *y2))
-        })
-        .flatten()
-        .collect();
-    let y_lines = coords
-        .iter()
-        .map(|(x1, y1)| {
-            coords
-                .iter()
-                .filter(move |(x2, y2)| y1 == y2 && x1 < x2)
-                .map(move |(x2, y2)| (*y1, *x1, *x2))
-        })
-        .flatten()
-        .collect();
+fn check(corner_1: usize, corner_3: usize, coords: &Vec<(i64, i64)>) -> bool {
+    // Check by filtering coords between corners; then check if any consecutive
+    // ones cross the rectangle.
+    let a1 = coords[corner_1];
+    let a3 = coords[corner_3];
 
-    (x_lines, y_lines)
+    let upper_left = (a1.0.min(a3.0), a1.1.min(a3.1));
+    let lower_right = (a1.0.max(a3.0), a1.1.max(a3.1));
+
+    for ((x1, y1), (x2, y2)) in coords.iter().circular_tuple_windows() {
+        if y1 == y2 {
+            // line horizontal
+            if !(y1 >= &lower_right.1
+                || y1 <= &upper_left.1
+                || (x1 <= &upper_left.0 && x2 <= &upper_left.0)
+                || (x1 >= &lower_right.0 && x2 >= &lower_right.0))
+            {
+                // println!(
+                //     "rejected horizontal of {:?},{:?} due to line {:?} {:?}",
+                //     upper_left,
+                //     lower_right,
+                //     (x1, y1),
+                //     (x2, y2)
+                // );
+                return false;
+            }
+        } else {
+            // line horizontal
+            if !(x1 >= &lower_right.0
+                || x1 <= &upper_left.0
+                || (y1 <= &upper_left.1 && y2 <= &upper_left.1)
+                || (y1 >= &lower_right.1 && y2 >= &lower_right.1))
+            {
+                // println!(
+                //     "rejected vertical of {:?},{:?} due to line {:?} {:?}",
+                //     upper_left,
+                //     lower_right,
+                //     (x1, y1),
+                //     (x2, y2)
+                // );
+                return false;
+            }
+        }
+    }
+    true
 }
 
 fn parse(input: &str) -> Vec<(i64, i64)> {