From ce13c17b1e7b088d659dc798a309ab7761962e94 Mon Sep 17 00:00:00 2001
From: Julius de Jeu <julius@voidcorp.nl>
Date: Mon, 13 Dec 2021 10:54:03 +0100
Subject: [PATCH] Day 13

---
 input/day13  | 936 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/day12.rs |  26 +-
 src/day13.rs | 152 +++++++++
 src/main.rs  |   5 +-
 4 files changed, 1105 insertions(+), 14 deletions(-)
 create mode 100644 input/day13
 create mode 100644 src/day13.rs

diff --git a/input/day13 b/input/day13
new file mode 100644
index 0000000..d5aa0a8
--- /dev/null
+++ b/input/day13
@@ -0,0 +1,936 @@
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+
+fold along x=655
+fold along y=447
+fold along x=327
+fold along y=223
+fold along x=163
+fold along y=111
+fold along x=81
+fold along y=55
+fold along x=40
+fold along y=27
+fold along y=13
+fold along y=6
\ No newline at end of file
diff --git a/src/day12.rs b/src/day12.rs
index 4526af8..7a4ce96 100644
--- a/src/day12.rs
+++ b/src/day12.rs
@@ -175,17 +175,17 @@ start-RW";
     }
 
     // These are very slow, so they are commented out.
-    #[test]
-    fn part2_test_3() -> anyhow::Result<()> {
-        let d = Day12::init(INPUT_3.to_string())?;
-        assert_eq!("3509", d.part2()?);
-        Ok(())
-    }
-
-    #[test]
-    fn part2_real() -> anyhow::Result<()> {
-        let d = Day12::init(crate::load_input("12")?)?;
-        assert_eq!("117095", d.part2()?);
-        Ok(())
-    }
+    // #[test]
+    // fn part2_test_3() -> anyhow::Result<()> {
+    //     let d = Day12::init(INPUT_3.to_string())?;
+    //     assert_eq!("3509", d.part2()?);
+    //     Ok(())
+    // }
+    //
+    // #[test]
+    // fn part2_real() -> anyhow::Result<()> {
+    //     let d = Day12::init(crate::load_input("12")?)?;
+    //     assert_eq!("117095", d.part2()?);
+    //     Ok(())
+    // }
 }
\ No newline at end of file
diff --git a/src/day13.rs b/src/day13.rs
new file mode 100644
index 0000000..62c540b
--- /dev/null
+++ b/src/day13.rs
@@ -0,0 +1,152 @@
+use std::collections::HashSet;
+use std::str::FromStr;
+use crate::Day;
+
+pub struct Day13 {
+    points: HashSet<(i32, i32)>,
+    folds: Vec<Fold>,
+}
+
+#[derive(Ord, PartialOrd, Eq, PartialEq, Copy, Clone, Debug)]
+enum Fold {
+    X(i32),
+    Y(i32),
+}
+
+impl FromStr for Fold {
+    type Err = ();
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let r = s.rsplit(' ').nth(0).ok_or_else(|| ())?;
+        let z = r.split('=').collect::<Vec<_>>();
+        match z[0] {
+            "x" => Ok(Fold::X(z[1].parse().map_err(|_| ())?)),
+            "y" => Ok(Fold::Y(z[1].parse().map_err(|_| ())?)),
+            _ => Err(()),
+        }
+    }
+}
+
+
+impl Day for Day13 {
+    fn init(content: String) -> anyhow::Result<Self> {
+        let l = content.lines();
+        let points = l.clone().take_while(|&x| x != "").map(|st| st.split(',')
+            .map(str::parse).flatten().collect::<Vec<i32>>()).map(|v| (v[0], v[1])).collect::<HashSet<_>>();
+
+        Ok(Self {
+            points,
+            folds: l.filter(|st| st.starts_with("fold along")).map(str::parse).flatten().collect::<Vec<Fold>>(),
+        })
+    }
+
+    fn part1(&self) -> anyhow::Result<String> {
+        let fold = self.folds[0];
+        let map = self.points.clone();
+        Ok(format!("{}", flip(map, fold).len()))
+    }
+
+    fn part2(&self) -> anyhow::Result<String> {
+        let r = self.folds.iter().fold(self.points.clone(), |a, &b| flip(a, b));
+        let max_x = r.iter().max_by(|&(xm, _), &(xn, _)| xm.cmp(xn)).ok_or_else(|| anyhow::Error::msg("X is empty!"))?;
+        let max_y = r.iter().max_by(|&(_, xm), &(_, xn)| xm.cmp(xn)).ok_or_else(|| anyhow::Error::msg("Y is empty!"))?;
+        let mut z = String::new();
+        for y in 0..=max_y.1 {
+            for x in 0..=max_x.0 {
+                if r.contains(&(x, y)) {
+                    z += "█";
+                } else {
+                    z += " ";
+                }
+            }
+            z += "\n";
+        }
+        Ok(format!("\n{}", z))
+    }
+}
+
+fn flip(set: HashSet<(i32, i32)>, f: Fold) -> HashSet<(i32, i32)> {
+    set.iter().map(|&e| flip_one(e, f)).collect()
+}
+
+fn flip_one((x, y): (i32, i32), f: Fold) -> (i32, i32) {
+    match f {
+        Fold::X(pos) => {
+            let new_x = if x > pos {
+                pos - x + pos
+            } else {
+                x
+            };
+            (new_x, y)
+        }
+        Fold::Y(pos) => {
+            let new_y = if y > pos {
+                pos - y + pos
+            } else {
+                y
+            };
+            (x, new_y)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashSet;
+    use crate::day13::{Day13, flip, flip_one, Fold};
+    use crate::day::Day;
+
+    const INPUT: &str = r"6,10
+0,14
+9,10
+0,3
+10,4
+4,11
+6,0
+6,12
+4,1
+0,13
+10,12
+3,4
+3,0
+8,4
+1,10
+2,14
+8,10
+9,0
+
+fold along y=7
+fold along x=5";
+
+    #[test]
+    fn flip_test() {
+        assert_eq!(flip_one((0, 0), Fold::X(3)), (0, 0));
+        assert_eq!(flip_one((3, 0), Fold::X(3)), (3, 0));
+        assert_eq!(flip_one((6, 0), Fold::X(3)), (0, 0));
+    }
+
+    #[test]
+    fn flip_set_test() {
+        let set = HashSet::from([(0, 3), (3, 2), (6, 3)]);
+        let r = flip(set, Fold::X(3));
+        assert!(r.contains(&(0, 3)));
+        assert!(r.contains(&(3, 2)));
+        assert!(!r.contains(&(6, 3)));
+        assert_eq!(r.len(), 2);
+    }
+
+    #[test]
+    fn part1_test() -> anyhow::Result<()> {
+        let d = Day13::init(INPUT.to_string())?;
+        assert_eq!("17", d.part1()?);
+        Ok(())
+    }
+
+    #[test]
+    fn part1_real() -> anyhow::Result<()> {
+        let d = Day13::init(crate::load_input("13")?)?;
+        assert_eq!("781", d.part1()?);
+        Ok(())
+    }
+}
+
diff --git a/src/main.rs b/src/main.rs
index b81e939..bb3d30c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -15,6 +15,7 @@ use crate::day09::Day09;
 use crate::day10::Day10;
 use crate::day11::Day11;
 use crate::day12::Day12;
+use crate::day13::Day13;
 
 mod day;
 mod day01;
@@ -29,6 +30,7 @@ mod day09;
 mod day10;
 mod day11;
 mod day12;
+mod day13;
 
 fn load_input(day: &str) -> Result<String> {
     read_to_string(format!("./input/day{}", day)).map_err(|x| x.into())
@@ -75,7 +77,8 @@ fn main() -> anyhow::Result<()> {
                                        Box::new(Day09::init(load_input("09")?)?),
                                        Box::new(Day10::init(load_input("10")?)?),
                                        Box::new(Day11::init(load_input("11")?)?),
-                                       Box::new(Day12::init(load_input("12")?)?),];
+                                       Box::new(Day12::init(load_input("12")?)?),
+                                       Box::new(Day13::init(load_input("13")?)?),];
 
     let _verbosity = matches.occurrences_of("v");
     if matches.is_present("all") {