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use std::{env, fs, num::ParseIntError, ops::Range, str::FromStr};
#[derive(Debug, Clone, Copy)]
struct IDRange(u64, u64);
#[derive(Debug)]
struct ParseIDRangeError;
impl From<ParseIntError> for ParseIDRangeError {
fn from(_: ParseIntError) -> Self {
Self
}
}
impl FromStr for IDRange {
type Err = ParseIDRangeError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let (start, end) = s.split_once('-').ok_or(ParseIDRangeError)?;
Ok(Self(start.parse()?, end.parse()?))
}
}
struct IDRangeIntoIter {
range: IDRange,
cur: u64,
}
impl Iterator for IDRangeIntoIter {
type Item = ID;
fn next(&mut self) -> Option<Self::Item> {
if self.cur <= self.range.1 {
let id = ID(self.cur);
self.cur += 1;
Some(id)
} else {
None
}
}
}
impl IntoIterator for IDRange {
type Item = ID;
type IntoIter = IDRangeIntoIter;
fn into_iter(self) -> Self::IntoIter {
Self::IntoIter {
cur: self.0,
range: self,
}
}
}
#[derive(Debug, PartialEq, Eq)]
struct ID(u64);
impl ID {
fn is_invalid(&self) -> bool {
let s = self.0.to_string();
s.len() % 2 == 0 && {
let (a, b) = s.split_at(s.len() / 2);
a == b
}
}
}
#[derive(Debug)]
enum Error {
BadArgument,
BadRange(String),
}
impl From<std::io::Error> for Error {
fn from(_: std::io::Error) -> Self {
Self::BadArgument
}
}
fn main() -> Result<(), Error> {
let x: Range<u32> = 0..99;
let mut args = env::args();
let input_path = args.nth(1).ok_or_else(|| Error::BadArgument)?;
let input = fs::read_to_string(input_path)?;
let ranges: Vec<IDRange> = input
.split_whitespace()
.flat_map(|s| s.split(','))
.filter(|s| s.len() != 0)
.map(|s| s.parse().map_err(|_| Error::BadRange(s.into())))
.collect::<Result<_, _>>()?;
let result: u64 = ranges
.iter()
.flat_map(|range| range.into_iter().filter(ID::is_invalid).map(|id| id.0))
.sum();
println!("Result: {}", result);
Ok(())
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parse_id_range() -> Result<(), ParseIDRangeError> {
let range: IDRange = "99-100".parse()?;
assert_eq!(range.0, 99);
assert_eq!(range.1, 100);
Ok(())
}
#[test]
fn id_range_into_iter() {
let range = IDRange(2, 4);
let ids: Vec<ID> = range.into_iter().collect();
assert_eq!(ids, vec![ID(2), ID(3), ID(4)]);
}
#[test]
fn id_is_valid() {
assert!(!ID(0).is_invalid());
assert!(!ID(1).is_invalid());
assert!(!ID(2).is_invalid());
assert!(!ID(10).is_invalid());
assert!(!ID(12).is_invalid());
assert!(!ID(21).is_invalid());
assert!(ID(11).is_invalid());
assert!(ID(5555).is_invalid());
}
}
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