Missed several updates. Working on 8 pt 2

day_06/src/lib.rs

@@ -0,0 +1,64 @@
+use nom::{
+    bytes::complete::tag,
+    character::complete::{
+        self, space0, space1,
+    },
+    multi::separated_list1,
+    sequence::{preceded, tuple},
+    IResult,
+};
+use std::iter::zip;
+
+fn parse_races(input: &str) -> IResult<&str, Vec<(u64, u64)>> {
+    let (input, times) = preceded(tuple((tag("Time:"),space1)), separated_list1(space1, complete::u64))(input)?;
+    let (input, distances) = preceded(tuple((tag("\nDistance:"),space1)), separated_list1(space1, complete::u64))(input)?;
+    Ok((input, zip(times, distances).collect()))
+}
+
+fn parse_races_alt(input: &str) -> IResult<&str, (u64, u64)> {
+    let (input, times) = preceded(tuple((tag("Time:"),space0)), complete::u64)(input)?;
+    let (input, distances) = preceded(tuple((tag("\nDistance:"),space0)), complete::u64)(input)?;
+    Ok((input, (times, distances)))
+}
+
+pub fn part1(input: &str) -> String {
+    let (_, races) = parse_races(input).unwrap();
+    races.into_iter().map(|(time, distance)| {
+        let upper_bound_full = (time as f64 + ((time as f64).powi(2) - 4.0 * distance as f64).sqrt()) / 2.0;
+        let upper_bound = if upper_bound_full - upper_bound_full.floor() == 0.0 {
+            upper_bound_full.floor() as u64 - 1
+        } else {
+            upper_bound_full.floor() as u64
+        };
+        let lower_bound_full = (time as f64 - ((time as f64).powi(2) - 4.0 * distance as f64).sqrt()) / 2.0;
+        let lower_bound = if lower_bound_full - lower_bound_full.ceil() == 0.0 {
+            lower_bound_full.ceil() as u64 + 1
+        } else {
+            lower_bound_full.ceil() as u64
+        };
+        upper_bound - lower_bound + 1
+    }).product::<u64>().to_string()
+}
+
+pub fn part2(input: &str) -> String {
+    let (_, (time, distance)) = parse_races_alt(input.replace(" ", "").as_str()).unwrap();
+    let upper_bound_full = (time as f64 + ((time as f64).powi(2) - 4.0 * distance as f64).sqrt()) / 2.0;
+    let upper_bound = if upper_bound_full - upper_bound_full.floor() == 0.0 {
+        upper_bound_full.floor() as u64 - 1
+    } else {
+        upper_bound_full.floor() as u64
+    };
+    let lower_bound_full = (time as f64 - ((time as f64).powi(2) - 4.0 * distance as f64).sqrt()) / 2.0;
+    let lower_bound = if lower_bound_full - lower_bound_full.ceil() == 0.0 {
+        lower_bound_full.ceil() as u64 + 1
+    } else {
+        lower_bound_full.ceil() as u64
+    };
+    (upper_bound - lower_bound + 1).to_string()
+}
+
+pub mod prelude {
+    pub use super::part1;
+    pub use super::part2;
+}
+