From 691b44d1e91740a3fe813ceea1bb5e3f13e7d06f Mon Sep 17 00:00:00 2001
From: Niklas Kapelle <niklas@kapelle.org>
Date: Wed, 13 Dec 2023 16:10:14 +0100
Subject: [PATCH] day 6

---
 input/6.txt   |  2 ++
 src/common.rs | 22 +++++++++++++++++++--
 src/main.rs   |  3 +++
 src/six.rs    | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+), 2 deletions(-)
 create mode 100644 input/6.txt
 create mode 100644 src/six.rs

diff --git a/input/6.txt b/input/6.txt
new file mode 100644
index 0000000..a15dea2
--- /dev/null
+++ b/input/6.txt
@@ -0,0 +1,2 @@
+Time:        62     64     91     90
+Distance:   553   1010   1473   1074
\ No newline at end of file
diff --git a/src/common.rs b/src/common.rs
index 4d7efa6..d0d4f32 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -1,5 +1,10 @@
-use std::{fs::File, io::{BufReader, BufRead}};
+use std::{
+    fs::File,
+    io::{BufRead, BufReader},
+    str::FromStr,
+};
 
+use regex::Regex;
 
 pub fn load_input(filepath: &str) -> Result<Vec<String>, Box<dyn std::error::Error>> {
     let file = File::open(filepath)?;
@@ -13,4 +18,17 @@ pub fn load_input(filepath: &str) -> Result<Vec<String>, Box<dyn std::error::Err
     }
 
     Ok(result)
-}
\ No newline at end of file
+}
+
+pub fn parse_nums<T>(s: &str) -> Vec<T>
+where
+    T: FromStr,
+{
+    let regex = Regex::new(r"(?m)(\d+)").unwrap();
+    let result = regex.captures_iter(s);
+
+    result
+        .map(|e| e.get(0).unwrap().as_str())
+        .flat_map(|e| e.parse::<T>())
+        .collect()
+}
diff --git a/src/main.rs b/src/main.rs
index 540350e..ef65f33 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,6 +6,7 @@ mod two;
 mod three;
 mod four; 
 mod five;
+mod six;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
@@ -22,6 +23,8 @@ fn main() {
         "4p2" => four::run_part2(),
         "5" => five::run(),
         "5p2" => five::run_part2(),
+        "6" => six::run(),
+        "6p2" => six::run_part2(),
         _ => Ok(-1),
     };
 
diff --git a/src/six.rs b/src/six.rs
new file mode 100644
index 0000000..baec2fc
--- /dev/null
+++ b/src/six.rs
@@ -0,0 +1,54 @@
+use crate::common::{load_input, parse_nums};
+
+fn parse_input(lines: &[String]) -> (Vec<u64>, Vec<u64>) {
+    (
+        parse_nums(lines.get(0).unwrap()),
+        parse_nums(lines.get(1).unwrap()),
+    )
+}
+
+fn distance_by_time_pressed(time_pressed: u64, race_time: u64) -> u64 {
+    let speed = (race_time - time_pressed);
+    return speed * time_pressed;
+}
+
+fn join_nums(nums: &[u64]) -> u64 {
+    nums.iter()
+        .map(|e| e.to_string())
+        .collect::<String>()
+        .parse()
+        .unwrap()
+}
+
+pub fn run_part2() -> Result<i32, Box<dyn std::error::Error>> {
+    let lines = load_input("./input/6.txt")?;
+    let (time, distance) = parse_input(&lines);
+    let new_time = join_nums(&time);
+    let new_dist = join_nums(&distance);
+
+    let res = (0..new_time)
+        .map(|pressed| distance_by_time_pressed(pressed, new_time))
+        .filter(|e| *e > new_dist)
+        .count();
+
+    Ok(res.try_into().unwrap())
+}
+
+pub fn run() -> Result<i32, Box<dyn std::error::Error>> {
+    let lines = load_input("./input/6.txt")?;
+    let (time, distance) = parse_input(&lines);
+
+    let res = time
+        .iter()
+        .zip(distance.iter())
+        .map(|e| {
+            (0..*e.0)
+                .map(|pressed| distance_by_time_pressed(pressed, *e.0))
+                .filter(|dist| *dist > *e.1)
+                .count()
+        })
+        .reduce(|acc, e| e * acc)
+        .unwrap();
+
+    Ok(res.try_into().unwrap())
+}