Day 6 done

input/day06.txt

@@ -0,0 +1,2 @@
+Time:        61     67     75     71
+Distance:   430   1036   1307   1150

src/day6.rs

@@ -0,0 +1,94 @@
+use std::io;
+
+fn split_string(str: &String) -> Vec<u64> {
+  let start = str.find(':').expect("No ':' in string") + 1;
+  str[start..]
+    .trim()
+    .split(' ')
+    .filter(|str| str.len() > 0)
+    .map(|str| str.parse().expect("Could not parse u32"))
+    .collect()
+}
+
+fn get_big_int(str: &String) -> u64 {
+  let start = str.find(':').expect("No ':' in string") + 1;
+  str[start..]
+    .trim()
+    .split(' ')
+    .filter(|str| str.len() > 0)
+    .collect::<Vec<&str>>()
+    .join("")
+    .parse()
+    .expect("Could not parse")
+}
+
+fn count_options(time: u64, dist: u64) -> u64 {
+  let a: f64 = 1.0;
+  let b: f64 = -1.0 * (time as f64);
+  let c: f64 = dist as f64;
+
+  let root_part = ((b * b) - (4.0 * a * c)).sqrt();
+
+  let root1 = ((-1.0 * b) + root_part) / (2.0 * a);
+  let root2 = ((-1.0 * b) - root_part) / (2.0 * a);
+
+  let minroot = root1.min(root2);
+  let maxroot = root1.max(root2);
+
+  let mut minroot_int: i64 = minroot.ceil() as i64;
+  let mut maxroot_int: i64 = maxroot.floor() as i64;
+
+  if minroot_int < 0 {
+    println!("Negative root: {} <- {}", minroot_int, minroot);
+    return 0;
+  }
+
+  if maxroot_int < 0 {
+    println!("Negative root: {} <- {}", maxroot_int, maxroot);
+    return 0;
+  }
+
+  if minroot_int as f64 == minroot {
+    minroot_int += 1;
+  }
+
+  if maxroot_int as f64 == maxroot {
+    maxroot_int -= 1;
+  }
+
+  return (maxroot_int - minroot_int + 1) as u64;
+}
+
+pub fn get_winning_combos() -> u64 {
+  let mut buffer = String::new();
+  assert_ne!(io::stdin().read_line(&mut buffer).unwrap(), 0);
+  let times = split_string(&buffer);
+
+  buffer = String::new();
+  assert_ne!(io::stdin().read_line(&mut buffer).unwrap(), 0);
+  let dists = split_string(&buffer);
+
+  let mut product = 1;
+
+  if times.len() != dists.len() {
+    println!("Times and distances are a different length");
+    return 0;
+  }
+
+  for i in 0..times.len() {
+    product *= count_options(times[i], dists[i]);
+  }
+
+  product
+}
+
+pub fn get_single_winning_combo() -> u64 {
+  let mut buffer = String::new();
+  assert_ne!(io::stdin().read_line(&mut buffer).unwrap(), 0);
+  let time = get_big_int(&buffer);
+
+  buffer = String::new();
+  assert_ne!(io::stdin().read_line(&mut buffer).unwrap(), 0);
+  let dist = get_big_int(&buffer);
+  count_options(time, dist)
+}

src/main.rs

@@ -5,6 +5,7 @@ mod day2;
 mod day3;
 mod day4;
 mod day5;
+mod day6;
 
 fn main() {
   let args: Vec<String> = env::args().collect();
@@ -23,6 +24,8 @@ fn main() {
     "day4b" => println!("Sum: {}", day4::get_card_points().1),
     "day5a" => println!("Min: {}", day5::get_lowest_location(false)),
     "day5b" => println!("Min: {}", day5::get_lowest_location(true)),
+    "day6a" => println!("Product: {}", day6::get_winning_combos()),
+    "day6b" => println!("Product: {}", day6::get_single_winning_combo()),
     _ => println!("Unrecognized day: {}", args[1]),
   }
 }