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@@ -0,0 +1,66 @@
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+use std::fs;
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+use std::env;
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+
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+use nom::IResult;
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+use nom::multi::separated_list1;
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+use nom::bytes::complete::tag;
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+use nom::character::complete::i64;
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+use nom::character::complete::space1;
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+use nom::character::complete::line_ending;
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+use nom::sequence::tuple;
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+use nom::sequence::preceded;
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+use nom::sequence::terminated;
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+
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+fn parse_input_data(input: &str) -> IResult<&str, (Vec<i64>, Vec<i64>)> {
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+ tuple((terminated(preceded(tuple((tag("Time:"), space1)),
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+ separated_list1(space1,i64)),
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+ line_ending),
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+ terminated(preceded(tuple((tag("Distance:"), space1)),
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+ separated_list1(space1,i64)),
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+ line_ending)
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+ ))(input)
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+}
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+
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+fn parse_leaderboard(input_data: &str) -> Result<(Vec<i64>,Vec<i64>), String> {
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+ match parse_input_data(input_data) {
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+ Ok((rest, data)) => if rest == "" {
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+ Ok(data)
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+ } else {
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+ Err(format!("Incomplete parse, remaining: {}", rest))
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+ },
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+ Err(error) => Err(error.to_string()),
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+ }
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+}
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+
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+fn solve_eq(t: f64, d: f64) -> Option<(f64,f64)> {
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+ let discr = t*t - 4.0*d;
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+ if discr >= 0.0 {
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+ return Some(((t - discr.sqrt())/2.0, (t + discr.sqrt())/2.0));
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+ }
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+ None
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+}
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+
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+fn integer_bounds(t: i64, d: i64) -> (i64, i64) {
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+ match solve_eq(t as f64, d as f64) {
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+ Some((x1,x2)) => ((x1+0.0000001).ceil() as i64, (x2-0.0000001).floor() as i64),
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+ None => (0,0)
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+ }
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+}
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+
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+
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+fn main() {
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+ let args: Vec<String> = env::args().collect();
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+ let file_path = &args[1];
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+ let input_data = fs::read_to_string(file_path).unwrap_or_else(
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+ |_|{panic!("Can't read file {}", file_path)});
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+ let (times,distances) = parse_leaderboard(&input_data).unwrap_or_else(
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+ |e|{panic!("Failed to parse almanac: {}", e)});
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+
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+ let times_strings:Vec<String> = times.into_iter().map(|x|{x.to_string()}).collect();
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+ let distances_strings:Vec<String> = distances.into_iter().map(|x|{x.to_string()}).collect();
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+
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+ let time = times_strings.join("").parse::<i64>().unwrap();
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+ let distance = distances_strings.join("").parse::<i64>().unwrap();
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+ let (min, max) = integer_bounds(time, distance);
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+ println!("{}", max - min + 1);
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+}
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