Add 2020 - Day 2 - Part 1

.idea/runConfigurations/2020___Day_02.xml

@@ -0,0 +1,18 @@
+<component name="ProjectRunConfigurationManager">
+  <configuration default="false" name="2020 - Day 02" type="CargoCommandRunConfiguration" factoryName="Cargo Command">
+    <option name="command" value="run --bin 02" />
+    <option name="workingDirectory" value="file://$PROJECT_DIR$/2020/02" />
+    <option name="channel" value="DEFAULT" />
+    <option name="requiredFeatures" value="true" />
+    <option name="allFeatures" value="false" />
+    <option name="emulateTerminal" value="false" />
+    <option name="withSudo" value="false" />
+    <option name="backtrace" value="SHORT" />
+    <envs />
+    <option name="isRedirectInput" value="false" />
+    <option name="redirectInputPath" value="" />
+    <method v="2">
+      <option name="CARGO.BUILD_TASK_PROVIDER" enabled="true" />
+    </method>
+  </configuration>
+</component>

2020/02/main.rs

@@ -0,0 +1,47 @@
+use std::error::Error;
+use std::str::FromStr;
+
+use utils::GenericError;
+
+#[path = "../utils/mod.rs"]
+mod utils;
+
+fn main() -> Result<(), Box<dyn Error>> {
+	let lines = utils::parse_input_lines::<PasswordRule>()?;
+	
+	let valid_passwords = lines.iter().filter(|x| x.is_valid()).count();
+	println!("Valid passwords: {}", valid_passwords);
+	
+	Ok(())
+}
+
+struct PasswordRule {
+	left_value: usize,
+	right_value: usize,
+	required_char: String,
+	actual_password: String
+}
+
+impl PasswordRule {
+	fn is_valid(&self) -> bool {
+		let count = self.actual_password.matches(self.required_char.as_str()).count();
+		return count >= self.left_value && count <= self.right_value;
+	}
+}
+
+impl FromStr for PasswordRule {
+	type Err = GenericError<'static>;
+	
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		let (s_range, s_rest) = s.split_once(' ').ok_or(GenericError::new("Missing space."))?;
+		let (s_min, s_max) = s_range.split_once('-').ok_or(GenericError::new("Missing dash in the left part of the input."))?;
+		let (s_char, s_password) = s_rest.split_once(": ").ok_or(GenericError::new("Missing colon followed by space in the right part of the input."))?;
+		
+		return Ok(PasswordRule {
+			left_value: s_min.parse::<usize>().map_err(|_| GenericError::new("Cannot parse first number."))?,
+			right_value: s_max.parse::<usize>().map_err(|_| GenericError::new("Cannot parse second number."))?,
+			required_char: s_char.to_string(),
+			actual_password: s_password.to_string()
+		})
+	}
+}

2020/Cargo.toml

@@ -6,3 +6,7 @@ edition = "2021"
 [[bin]]
 name = "01"
 path = "01/main.rs"
+
+[[bin]]
+name = "02"
+path = "02/main.rs"

2020/utils/mod.rs

@@ -1,4 +1,5 @@
 use std::error::Error;
+use std::fmt::{Display, Formatter};
 use std::fs::File;
 use std::io;
 use std::io::{BufRead, BufReader};
@@ -12,3 +13,22 @@ pub fn read_input_lines() -> Result<Vec<String>, io::Error> {
 pub fn parse_input_lines<T : FromStr>() -> Result<Vec<T>, Box<dyn Error>> where <T as FromStr>::Err : Into<Box<dyn Error>> {
 	return read_input_lines()?.iter().map(|line| line.parse::<T>()).collect::<Result<Vec<T>, T::Err>>().map_err(Into::into);
 }
+
+#[derive(Debug)]
+pub struct GenericError<'a> {
+	pub message: &'a str
+}
+
+impl<'a> GenericError<'a> {
+	pub fn new(message: &'a str) -> GenericError<'a> {
+		GenericError { message }
+	}
+}
+
+impl Display for GenericError<'_> {
+	fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+		write!(f, "Parse error: {}", self.message)
+	}
+}
+
+impl Error for GenericError<'_> {}

README.md

@@ -38,6 +38,7 @@ The versions should not matter, but I used Visual Studio 2019 with `MSVC v142 (1
 | 2015 |  01 | NASM x64 |
 | 2015 |  02 | NASM x64 |
 | 2020 |  01 | Rust     |
+| 2020 |  02 | Rust     |
 | 2021 |  01 | Kotlin   |
 | 2021 |  02 | Kotlin   |
 | 2021 |  03 | Kotlin   |