104 lines
2.1 KiB
Rust
104 lines
2.1 KiB
Rust
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use std::collections::HashMap;
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use std::fmt;
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use super::Result;
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const INPUT: &str = include_str!("../input/day03.txt");
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pub fn run() -> Result<()> {
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println!("part 1: {}", part1(INPUT)?);
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Ok(())
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}
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#[derive(Debug)]
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struct ParseError {
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line: String,
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}
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impl ParseError {
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fn new(line: &str) -> Self {
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ParseError {
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line: line.to_string(),
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}
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}
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}
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impl fmt::Display for ParseError {
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fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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write!(f, "{}", self.line)
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}
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}
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impl std::error::Error for ParseError {
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fn description(&self) -> &str {
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&self.line
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}
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}
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fn parse(line: &str) -> Option<(usize, usize, usize, usize)> {
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// remove '#XXX @ ' start of line
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let line = &line[(line.find(" @ ")? + 3)..];
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// parse 'x,y: NNxNN
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let comma = line.find(',')?;
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let colon = line.find(':')?;
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let x = line[..comma].parse().ok()?;
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let y = line[(comma + 1)..colon].parse().ok()?;
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// reduce line to 'NNxNN'
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let line = &line[(colon + 2)..];
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let sep = line.find('x')?;
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let width = line[..sep].parse().ok()?;
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let height = line[(sep + 1)..].parse().ok()?;
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Some((x, y, width, height))
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}
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fn part1(input: &str) -> Result<u64> {
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let mut res = 0;
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let mut map: HashMap<(usize, usize), u64> = HashMap::default();
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for line in input.lines() {
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let (x, y, width, height) = parse(line).ok_or(ParseError::new(line))?;
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for i in 0..width {
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for j in 0..height {
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let x = x + i;
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let y = y + j;
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// add tissue patch at coordinates (x, y)
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let entry = map.entry((x, y)).or_default();
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*entry += 1;
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// count overlap the first time only
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if *entry == 2 {
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res += 1;
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}
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}
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}
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}
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Ok(res)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn part1_provided() {
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let input = "#1 @ 1,3: 4x4
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#2 @ 3,1: 4x4
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#3 @ 5,5: 2x2
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";
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assert_eq!(part1(input).unwrap(), 4);
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}
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#[test]
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fn part1_real() {
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assert_eq!(part1(INPUT).unwrap(), 114946);
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}
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}
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