Day 10. I feel like my software development practices are getting worse as this goes on.

src/bin/day10.rs

@@ -0,0 +1,83 @@
+const TEST_DATA: &str = include_str!("../../data/day10t.txt");
+const REAL_DATA: &str = include_str!("../../data/day10a.txt");
+
+#[derive(Debug)]
+enum ParseResult {
+    IncompleteLine(Vec<char>),
+    IllegalCharacter(char),
+    UnexpectedClose(char),
+    Success,
+}
+
+fn flip(c: char) -> char {
+    match c {
+        '(' => ')',
+        '[' => ']',
+        '{' => '}',
+        '<' => '>',
+        _ => c,
+    }
+}
+
+fn parse_line(s: &str) -> ParseResult {
+    let mut open_stack = Vec::new();
+
+    for c in s.chars() {
+        match c {
+            '(' | '[' | '{' | '<' => open_stack.push(flip(c)),
+            ')' | ']' | '}' | '>' => match open_stack.pop() {
+                None => return ParseResult::UnexpectedClose(c),
+                Some(expected) if expected == c => {}
+                Some(_) => return ParseResult::UnexpectedClose(c),
+            },
+            _ => return ParseResult::IllegalCharacter(c),
+        }
+    }
+
+    if open_stack.is_empty() {
+        ParseResult::Success
+    } else {
+        ParseResult::IncompleteLine(open_stack)
+    }
+}
+
+fn process_file(file_data: &str) -> (u64, u64) {
+    let mut part1_score = 0;
+    let mut part2_scores = Vec::new();
+
+    for line in file_data.lines() {
+        match parse_line(line) {
+            ParseResult::UnexpectedClose(')') => part1_score += 3,
+            ParseResult::UnexpectedClose(']') => part1_score += 57,
+            ParseResult::UnexpectedClose('}') => part1_score += 1197,
+            ParseResult::UnexpectedClose('>') => part1_score += 25137,
+
+            ParseResult::IncompleteLine(stack) => {
+                let mut new_score = 0;
+
+                for c in stack.iter().rev() {
+                    match c {
+                        ')' => new_score = new_score * 5 + 1,
+                        ']' => new_score = new_score * 5 + 2,
+                        '}' => new_score = new_score * 5 + 3,
+                        '>' => new_score = new_score * 5 + 4,
+                        _ => new_score *= 5,
+                    }
+                }
+
+                part2_scores.push(new_score);
+            }
+
+            _ => {}
+        }
+    }
+
+    part2_scores.sort_unstable();
+
+    (part1_score, part2_scores[part2_scores.len() / 2])
+}
+
+fn main() {
+    println!("Test result: {:?}", process_file(TEST_DATA));
+    println!("Real result: {:?}", process_file(REAL_DATA));
+}