From 05b76ae3658332b685982a1cb62697d9016a873e Mon Sep 17 00:00:00 2001
From: Adrian Groh <adrian.groh@t-online.de>
Date: Tue, 10 Dec 2024 09:31:51 +0100
Subject: [PATCH] Add day10

---
 day10/Cargo.lock  |  7 +++++
 day10/Cargo.toml  |  6 ++++
 day10/src/main.rs | 78 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 day10/Cargo.lock
 create mode 100644 day10/Cargo.toml
 create mode 100644 day10/src/main.rs

diff --git a/day10/Cargo.lock b/day10/Cargo.lock
new file mode 100644
index 0000000..6b69a8f
--- /dev/null
+++ b/day10/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "day10"
+version = "0.1.0"
diff --git a/day10/Cargo.toml b/day10/Cargo.toml
new file mode 100644
index 0000000..3c916ef
--- /dev/null
+++ b/day10/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "day10"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/day10/src/main.rs b/day10/src/main.rs
new file mode 100644
index 0000000..9b4f02a
--- /dev/null
+++ b/day10/src/main.rs
@@ -0,0 +1,78 @@
+use std::collections::HashSet;
+
+fn parse(input: &str) -> Vec<Vec<u32>> {
+    input
+        .lines()
+        .map(|line| line.chars().map(|c| c.to_digit(10).unwrap_or(10)).collect())
+        .collect()
+}
+
+fn get_score(pos: &(usize, usize), prev: &isize, map: &[Vec<u32>]) -> HashSet<(usize, usize)> {
+    let mut res = HashSet::new();
+    let Some(Some(val)) = map.get(pos.0).map(|x| x.get(pos.1)) else {
+        return res;
+    };
+    if *val != (prev + 1) as u32 {
+        return res;
+    }
+    if val == &9 && prev == &8 {
+        res.insert(*pos);
+        return res;
+    }
+    res.extend(get_score(
+        &(pos.0.overflowing_sub(1).0, pos.1),
+        &(*val as isize),
+        map,
+    ));
+    res.extend(get_score(&(pos.0 + 1, pos.1), &(*val as isize), map));
+    res.extend(get_score(
+        &(pos.0, pos.1.overflowing_sub(1).0),
+        &(*val as isize),
+        map,
+    ));
+    res.extend(get_score(&(pos.0, pos.1 + 1), &(*val as isize), map));
+    res
+}
+
+fn get_rating(pos: &(usize, usize), prev: &isize, map: &[Vec<u32>]) -> usize {
+    let Some(Some(val)) = map.get(pos.0).map(|x| x.get(pos.1)) else {
+        return 0;
+    };
+    if *val != (prev + 1) as u32 {
+        return 0;
+    }
+    if val == &9 && prev == &8 {
+        return 1;
+    }
+    get_rating(&(pos.0.overflowing_sub(1).0, pos.1), &(*val as isize), map)
+        + get_rating(&(pos.0 + 1, pos.1), &(*val as isize), map)
+        + get_rating(&(pos.0, pos.1.overflowing_sub(1).0), &(*val as isize), map)
+        + get_rating(&(pos.0, pos.1 + 1), &(*val as isize), map)
+}
+
+fn part12(input: &[Vec<u32>], part1: bool) -> usize {
+    let trailheads: Vec<_> = input
+        .iter()
+        .enumerate()
+        .flat_map(|(l_idx, l)| {
+            l.iter()
+                .enumerate()
+                .filter(|(_, c)| c == &&0)
+                .map(move |(c_idx, _)| (l_idx, c_idx))
+        })
+        .collect();
+    if part1 {
+        trailheads
+            .iter()
+            .flat_map(|t| get_score(t, &-1, input))
+            .count()
+    } else {
+        trailheads.iter().map(|t| get_rating(t, &-1, input)).sum()
+    }
+}
+
+fn main() {
+    let input = parse(include_str!("../input.txt"));
+    println!("{}", part12(&input, true));
+    println!("{}", part12(&input, false));
+}