day 2

.gitignore

@@ -22,4 +22,5 @@ Cargo.lock
 
 *.exe
 
-input.txt
+data.txt
+test-data.txt

day02/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "day02"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+regex = "1.11.1"

day02/src/main.rs

@@ -0,0 +1,117 @@
+// Day 02: Red-Nosed Reports
+
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::path::Path;
+use regex::Regex;
+
+const FILE_NAME: &str = "./data.txt";
+
+enum Direction {
+  Unknown,
+  Increasing,
+  Decreasing
+}
+
+fn solve() {
+  println!("Day 02: Part 1");
+  println!("GOAL: Analyze the unusual data from the engineers.");
+  println!("ANSWER: How many reports are safe?");
+
+  let mut valid_reports = 0;
+
+  let re_split = Regex::new(r"(\s+)").expect("Invalid regex");
+    if let Ok(lines) = read_lines(FILE_NAME) {
+    for line in lines.flatten() {
+      let values: Vec<_> = re_split.split(&line).map(|f| f.parse::<u32>().unwrap()).collect();
+
+      let is_valid = is_valid_report(&values);
+
+      // println!("Report {} {} valid", line, if is_valid { "is" } else { "is NOT" });
+
+      if is_valid {
+        valid_reports += 1;
+      }
+    }
+  }
+  println!("Valid reports = {valid_reports}");
+
+  println!("-----------");
+  println!("Day 02: Part 2");
+  println!("GOAL: Update your analysis by handling situations where the Problem Dampener can remove a single level from unsafe reports.");
+  println!("ANSWER: How many reports are now safe?");
+
+  valid_reports = 0;
+  if let Ok(lines) = read_lines(FILE_NAME) {
+    for line in lines.flatten() {
+      let values: Vec<_> = re_split.split(&line).map(|f| f.parse::<u32>().unwrap()).collect();
+
+      let is_valid = is_any_valid_report(&values);
+
+      println!("Report {} {} valid", line, if is_valid { "is" } else { "is NOT" });
+
+      if is_valid {
+        valid_reports += 1;
+      }
+    }
+  }  
+  println!("Valid reports = {valid_reports}");
+
+}
+
+fn is_valid_report (values: &Vec<u32>) -> bool {
+  let mut direction = Direction::Unknown;
+  // println!("Checking values {:?}", values);
+  let mut last_report = *values.first().unwrap();
+
+  for r in &values[1..] {
+    let report = *r;
+
+    if matches!(direction, Direction::Unknown) {
+      direction =
+      if report > last_report { Direction::Increasing }
+      else { Direction::Decreasing };
+    }
+
+    if report == last_report { return false; };
+    if matches!(direction, Direction::Increasing) && (report < last_report || report > last_report + 3) { return false };
+    if matches!(direction, Direction::Decreasing) && (report > last_report || report + 3 < last_report) { return false };
+
+    last_report = report;
+  };
+
+  return true;
+}
+
+fn is_any_valid_report (values: &Vec<u32>) -> bool {
+  if is_valid_report(values) { return true; }
+  let length = values.len();
+  for idx in 0..length {
+    if is_valid_report(&copy_except(values, idx)) { return true; }
+  }
+
+  return false;
+}
+
+fn copy_except (values: &Vec<u32>, exclude_idx: usize) -> Vec<u32> {
+  let mut new_values: Vec<u32> = Vec::new();
+  let mut idx = 0;
+  for value in values {
+    if idx != exclude_idx {
+      new_values.push(*value);
+    }
+    idx += 1;
+  }
+  // println!("copied new values {:?}", new_values);
+  return new_values;
+}
+
+fn main() {
+  solve();
+}
+
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where P: AsRef<Path>, {
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}

main.rs.template

@@ -1,12 +1,20 @@
 // Day #DAY#: #TITLE#
 
-use std::env;
+use std::fs::File;
-use std::fs;
+use std::io::{self, BufRead};
+use std::path::Path;
+use regex::Regex;
 
 fn solve_part1() {
   println!("Day #DAY#: Part 1");
   println!("GOAL: #GOAL1#");
   println!("ANSWER: #ANSWER1#");
+
+  if let Ok(lines) = read_lines("./data.txt") {
+    for line in lines.flatten() {
+      ...
+    }
+  }
 }
 
 fn solve_part2 () {
@@ -19,3 +27,9 @@ fn main() {
   solve_part1()
   solve_part2()
 }
+
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where P: AsRef<Path>, {
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}

makefile

@@ -5,6 +5,7 @@ init:
 	cargo new day$(day)
 	sed 's/#DAY#/$(day)/g' main.rs.template | sed 's/#TITLE#/$(title)/g' > day$(day)/src/main.rs
 	touch day$(day)/data.txt
+	cd day$(day) && cargo add regex
 
 build:
 	cd ./day$(day) &&	cargo build