Completed day 7 part 1

inputs/7.txt

@@ -0,0 +1,101 @@
+Step I must be finished before step Q can begin.
+Step B must be finished before step O can begin.
+Step J must be finished before step M can begin.
+Step W must be finished before step Y can begin.
+Step U must be finished before step X can begin.
+Step T must be finished before step Q can begin.
+Step G must be finished before step M can begin.
+Step K must be finished before step C can begin.
+Step F must be finished before step Z can begin.
+Step D must be finished before step A can begin.
+Step N must be finished before step Y can begin.
+Step Y must be finished before step Q can begin.
+Step Q must be finished before step Z can begin.
+Step V must be finished before step E can begin.
+Step A must be finished before step X can begin.
+Step E must be finished before step C can begin.
+Step O must be finished before step R can begin.
+Step P must be finished before step L can begin.
+Step H must be finished before step R can begin.
+Step M must be finished before step R can begin.
+Step C must be finished before step Z can begin.
+Step R must be finished before step L can begin.
+Step L must be finished before step S can begin.
+Step S must be finished before step X can begin.
+Step Z must be finished before step X can begin.
+Step T must be finished before step O can begin.
+Step D must be finished before step Z can begin.
+Step P must be finished before step R can begin.
+Step M must be finished before step Z can begin.
+Step L must be finished before step Z can begin.
+Step W must be finished before step N can begin.
+Step Q must be finished before step R can begin.
+Step P must be finished before step C can begin.
+Step U must be finished before step O can begin.
+Step F must be finished before step O can begin.
+Step K must be finished before step X can begin.
+Step G must be finished before step K can begin.
+Step M must be finished before step C can begin.
+Step Y must be finished before step Z can begin.
+Step A must be finished before step O can begin.
+Step D must be finished before step P can begin.
+Step K must be finished before step S can begin.
+Step I must be finished before step E can begin.
+Step G must be finished before step F can begin.
+Step S must be finished before step Z can begin.
+Step N must be finished before step V can begin.
+Step F must be finished before step D can begin.
+Step A must be finished before step Z can begin.
+Step F must be finished before step X can begin.
+Step T must be finished before step Y can begin.
+Step W must be finished before step H can begin.
+Step D must be finished before step H can begin.
+Step W must be finished before step G can begin.
+Step J must be finished before step X can begin.
+Step T must be finished before step X can begin.
+Step U must be finished before step R can begin.
+Step O must be finished before step P can begin.
+Step L must be finished before step X can begin.
+Step I must be finished before step B can begin.
+Step M must be finished before step L can begin.
+Step C must be finished before step R can begin.
+Step R must be finished before step X can begin.
+Step F must be finished before step N can begin.
+Step V must be finished before step H can begin.
+Step K must be finished before step A can begin.
+Step W must be finished before step O can begin.
+Step U must be finished before step Q can begin.
+Step O must be finished before step C can begin.
+Step K must be finished before step V can begin.
+Step R must be finished before step S can begin.
+Step E must be finished before step S can begin.
+Step J must be finished before step A can begin.
+Step E must be finished before step X can begin.
+Step K must be finished before step Y can begin.
+Step Y must be finished before step X can begin.
+Step P must be finished before step Z can begin.
+Step W must be finished before step X can begin.
+Step Y must be finished before step A can begin.
+Step V must be finished before step X can begin.
+Step O must be finished before step M can begin.
+Step I must be finished before step J can begin.
+Step W must be finished before step L can begin.
+Step I must be finished before step G can begin.
+Step D must be finished before step O can begin.
+Step D must be finished before step N can begin.
+Step M must be finished before step X can begin.
+Step I must be finished before step R can begin.
+Step Y must be finished before step M can begin.
+Step F must be finished before step M can begin.
+Step U must be finished before step M can begin.
+Step Y must be finished before step H can begin.
+Step K must be finished before step D can begin.
+Step N must be finished before step O can begin.
+Step H must be finished before step S can begin.
+Step G must be finished before step L can begin.
+Step T must be finished before step D can begin.
+Step J must be finished before step N can begin.
+Step K must be finished before step M can begin.
+Step K must be finished before step P can begin.
+Step E must be finished before step R can begin.
+Step N must be finished before step H can begin.

inputs/7_test.txt

@@ -0,0 +1,7 @@
+Step C must be finished before step A can begin.
+Step C must be finished before step F can begin.
+Step A must be finished before step B can begin.
+Step A must be finished before step D can begin.
+Step B must be finished before step E can begin.
+Step D must be finished before step E can begin.
+Step F must be finished before step E can begin.

src/day7.rs

@@ -0,0 +1,132 @@
+extern crate regex;
+
+use std::error::Error;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+use std::fmt;
+use std::collections::HashMap;
+
+use regex::{Regex, Captures};
+
+const INPUT: &str = "inputs/7.txt";
+
+#[derive(Debug, Clone, PartialEq)]
+struct MalformedInstruction {
+    details: String
+}
+
+impl MalformedInstruction {
+    fn new(msg: &str) -> MalformedInstruction {
+        MalformedInstruction{ details: msg.to_string() }
+    }
+}
+
+impl fmt::Display for MalformedInstruction {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.details)
+    }
+}
+
+impl Error for MalformedInstruction {
+    fn description(&self) -> &str {
+        &self.details
+    }
+}
+
+pub fn solve_part1() -> Result<String, Box<Error>> {
+    let mut instructions = read_instructions(INPUT)?;
+    Ok(get_step_sequence(&mut instructions))
+}
+
+fn read_instructions(filename: &str) -> Result<HashMap<String, Vec<String>>, Box<Error>> {
+    let mut instructions: HashMap<String, Vec<String>> = HashMap::new();
+    lazy_static! {
+        static ref INSTRUCTION_REGEX: Regex = Regex::new(
+            r"Step (?P<dependency>\w) must be finished before step (?P<step>\w) can begin."
+        ).unwrap();
+    }
+    let file = File::open(filename)?;
+    for (index, line) in BufReader::new(file).lines().enumerate() {
+        match INSTRUCTION_REGEX.captures(&line?) {
+            Some(captures) => {
+                let step = get_captured_field(&captures, "step")?.parse()?;
+                let dependency: String = get_captured_field(&captures, "dependency")?.parse()?;
+                instructions.entry(dependency.clone()).or_insert(Vec::new());
+                let dependencies = instructions.entry(step).or_insert(Vec::new());
+                dependencies.push(dependency);
+            },
+            None => return Err(Box::new(MalformedInstruction {
+                details: "Malformed instruction line, no fields could be found".to_string()
+            })),
+        };
+    }
+    Ok(instructions)
+}
+
+fn get_captured_field(captures: &Captures, field: &str) -> Result<String, Box<Error>> {
+    match captures.name(field) {
+        Some(capture) => Ok(String::from(capture.as_str())),
+        None => return Err(Box::new(MalformedInstruction {
+            details: format!("Malformed instruction line, field {} could not be found", field)
+        }))
+    }
+}
+
+fn get_step_sequence(instructions: &mut HashMap<String, Vec<String>>) -> String {
+    let mut sequence: Vec<String> = Vec::new();
+    loop {
+        let mut available: Vec<String> = instructions
+            .iter()
+            .filter(|(_, dependencies)| dependencies.len() == 0)
+            .map(|(step, _)| step.clone())
+            .collect();
+        if available.len() == 0 { break; }
+        available.sort();
+        available.reverse();
+        let next = available.pop().unwrap();
+        instructions.remove(&next);
+        for dependencies in instructions.values_mut() {
+            match dependencies.iter().position(|d| *d == next) {
+                Some(index) => { dependencies.remove(index); },
+                None => ()
+            }
+        }
+        sequence.push(next);
+    }
+    sequence.join("")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TEST_INPUT: &str = "inputs/7_test.txt";
+
+    #[test]
+    fn reads_instructions_file() {
+        let expected: HashMap<String, Vec<String>> = [
+            ("A".to_string(), vec!["C".to_string()]),
+            ("F".to_string(), vec!["C".to_string()]),
+            ("C".to_string(), vec![]),
+            ("B".to_string(), vec!["A".to_string()]),
+            ("D".to_string(), vec!["A".to_string()]),
+            ("E".to_string(), vec!["B".to_string(), "D".to_string(), "F".to_string()]),
+
+        ].iter().cloned().collect();
+        assert_eq!(read_instructions(TEST_INPUT).unwrap(), expected);
+    }
+
+    #[test]
+    fn gets_step_sequence() {
+        let mut instructions: HashMap<String, Vec<String>> = [
+            ("A".to_string(), vec!["C".to_string()]),
+            ("F".to_string(), vec!["C".to_string()]),
+            ("C".to_string(), vec![]),
+            ("B".to_string(), vec!["A".to_string()]),
+            ("D".to_string(), vec!["A".to_string()]),
+            ("E".to_string(), vec!["B".to_string(), "D".to_string(), "F".to_string()]),
+
+        ].iter().cloned().collect();
+        assert_eq!(get_step_sequence(&mut instructions), "CABDFE");
+    }
+}

src/main.rs

@@ -7,6 +7,7 @@ mod day3;
 mod day4;
 mod day5;
 mod day6;
+mod day7;
 
 fn main() {
     // println!("Day 1:");
@@ -24,7 +25,9 @@ fn main() {
     // println!("Day 5:");
     // println!("{}", day5::solve_part1().unwrap());
     // println!("{}", day5::solve_part2().unwrap());
-    println!("Day 6:");
-    println!("{}", day6::solve_part1().unwrap());
-    println!("{}", day6::solve_part2().unwrap());
+    // println!("Day 6:");
+    // println!("{}", day6::solve_part1().unwrap());
+    // println!("{}", day6::solve_part2().unwrap());
+    println!("Day 7:");
+    println!("{}", day7::solve_part1().unwrap());
 }