[2018][rust][3.0]
diff --git a/2018/rust/Cargo.lock b/2018/rust/Cargo.lock
index ec1441e..0d00eb6 100644
--- a/2018/rust/Cargo.lock
+++ b/2018/rust/Cargo.lock
@@ -1,4 +1,95 @@
[[package]]
name = "advent_of_code_2018"
version = "0.1.0"
+dependencies = [
+ "regex 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+[[package]]
+name = "aho-corasick"
+version = "0.6.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "memchr 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "cfg-if"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "lazy_static"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "libc"
+version = "0.2.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "memchr"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "regex"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "aho-corasick 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "utf8-ranges 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ucd-util 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "thread_local"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "ucd-util"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "utf8-ranges"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "version_check"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[metadata]
+"checksum aho-corasick 0.6.9 (registry+https://github.com/rust-lang/crates.io-index)" = "1e9a933f4e58658d7b12defcf96dc5c720f20832deebe3e0a19efd3b6aaeeb9e"
+"checksum cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "082bb9b28e00d3c9d39cc03e64ce4cea0f1bb9b3fde493f0cbc008472d22bdf4"
+"checksum lazy_static 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a374c89b9db55895453a74c1e38861d9deec0b01b405a82516e9d5de4820dea1"
+"checksum libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)" = "10923947f84a519a45c8fefb7dd1b3e8c08747993381adee176d7a82b4195311"
+"checksum memchr 2.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0a3eb002f0535929f1199681417029ebea04aadc0c7a4224b46be99c7f5d6a16"
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+"checksum version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "914b1a6776c4c929a602fafd8bc742e06365d4bcbe48c30f9cca5824f70dc9dd"
diff --git a/2018/rust/Cargo.toml b/2018/rust/Cargo.toml
index 0d393ec..724709c 100644
--- a/2018/rust/Cargo.toml
+++ b/2018/rust/Cargo.toml
@@ -5,3 +5,4 @@ authors = ["Alpha Chen <alpha.chen@gmail.com>"]
edition = "2018"
[dependencies]
+regex = "1"
diff --git a/2018/rust/src/bin/day_03.rs b/2018/rust/src/bin/day_03.rs
new file mode 100644
index 0000000..c636e37
--- /dev/null
+++ b/2018/rust/src/bin/day_03.rs
@@ -0,0 +1,120 @@
+use std::collections::HashMap;
+use std::error::Error;
+use std::io::{self, Read};
+use std::str::FromStr;
+
+use regex::Regex;
+
+fn main() -> Result<(), Box<Error>> {
+ let mut input = String::new();
+ io::stdin().read_to_string(&mut input)?;
+
+ let output = solve(&input)?;
+ println!("{}", output);
+
+ Ok(())
+}
+
+fn solve(input: &str) -> Result<String, Box<Error>> {
+ let claims: Vec<_> = input
+ .lines()
+ .map(str::trim)
+ .map(Claim::from_str)
+ .collect::<Result<_, _>>()?;
+ let fabric = claims.iter().fold(HashMap::new(), |mut fabric, claim| {
+ for square_inch in claim.square_inches() {
+ fabric
+ .entry(square_inch)
+ .and_modify(|count| *count += 1)
+ .or_insert(1);
+ }
+ fabric
+ });
+ let output = fabric.values().filter(|&&count| count > 1).count();
+ Ok(output.to_string())
+}
+
+#[test]
+fn test_solve() {
+ let input = r"
+ #1 @ 1,3: 4x4
+ #2 @ 3,1: 4x4
+ #3 @ 5,5: 2x2
+ "
+ .trim();
+
+ assert_eq!(&solve(input).unwrap(), "4");
+}
+
+#[derive(Debug, PartialEq, Eq)]
+struct Claim {
+ id: usize,
+ x: usize,
+ y: usize,
+ width: usize,
+ height: usize,
+}
+
+impl Claim {
+ fn square_inches(&self) -> impl Iterator<Item = (usize, usize)> + '_ {
+ (self.x..self.x + self.width)
+ .flat_map(move |x| (self.y..self.y + self.height).map(move |y| (x, y)))
+ }
+}
+
+#[test]
+fn test_claim_square_inches() {
+ let claim = Claim {
+ id: 1,
+ x: 2,
+ y: 3,
+ width: 4,
+ height: 4,
+ };
+ let square_inches: Vec<_> = claim.square_inches().collect();
+ assert_eq!(square_inches.len(), 16);
+ assert!(square_inches.contains(&(2, 3)));
+ assert!(square_inches.contains(&(5, 3)));
+ assert!(square_inches.contains(&(5, 6)));
+ assert!(square_inches.contains(&(2, 6)));
+}
+
+impl FromStr for Claim {
+ type Err = Box<Error>;
+
+ fn from_str(s: &str) -> Result<Self, Self::Err> {
+ let re =
+ Regex::new(r"^#(?P<id>\d+) @ (?P<x>\d+),(?P<y>\d+): (?P<width>\d+)x(?P<height>\d+)$")
+ .unwrap();
+
+ let captures = re.captures(s).unwrap();
+ let id = captures.name("id").unwrap().as_str().parse()?;
+ let x = captures.name("x").unwrap().as_str().parse()?;
+ let y = captures.name("y").unwrap().as_str().parse()?;
+ let width = captures.name("width").unwrap().as_str().parse()?;
+ let height = captures.name("height").unwrap().as_str().parse()?;
+
+ Ok(Claim {
+ id,
+ x,
+ y,
+ width,
+ height,
+ })
+ }
+}
+
+#[test]
+fn test_claim_from_str() {
+ let claim = Claim::from_str("#1 @ 1,3: 4x4").unwrap();
+ assert_eq!(
+ claim,
+ Claim {
+ id: 1,
+ x: 1,
+ y: 3,
+ width: 4,
+ height: 4
+ }
+ );
+}