1 files changed, 109 insertions, 0 deletions
diff --git a/src/bin/2021/day10.rs b/src/bin/2021/day10.rs
new file mode 100644
index 0000000..d7b5f48
--- /dev/null
+++ b/src/bin/2021/day10.rs
@@ -0,0 +1,109 @@
+use advent_of_code::prelude::*;
+
+pub fn parse(fh: File) -> Result<impl Iterator<Item = String>> {
+    Ok(parse::raw_lines(fh))
+}
+
+pub fn part1(lines: impl Iterator<Item = String>) -> Result<u64> {
+    let mut total = 0;
+    for line in lines {
+        let mut open = vec![];
+        for c in line.chars() {
+            match c {
+                '{' | '(' | '[' | '<' => {
+                    open.push(c);
+                }
+                '}' | ')' | ']' | '>' => {
+                    let c_open = open.pop();
+                    if let Some(c_open) = c_open {
+                        let expected = match c_open {
+                            '{' => '}',
+                            '(' => ')',
+                            '[' => ']',
+                            '<' => '>',
+                            _ => unreachable!(),
+                        };
+                        if c != expected {
+                            total += match c {
+                                '}' => 1197,
+                                ')' => 3,
+                                ']' => 57,
+                                '>' => 25137,
+                                _ => unreachable!(),
+                            };
+                            break;
+                        }
+                    } else {
+                        break;
+                    }
+                }
+                _ => break,
+            }
+        }
+    }
+    Ok(total)
+}
+
+pub fn part2(lines: impl Iterator<Item = String>) -> Result<u64> {
+    let mut scores = vec![];
+    for line in lines {
+        let mut open = vec![];
+        let mut skip = false;
+        for c in line.chars() {
+            match c {
+                '{' | '(' | '[' | '<' => {
+                    open.push(c);
+                }
+                '}' | ')' | ']' | '>' => {
+                    let c_open = open.pop();
+                    if let Some(c_open) = c_open {
+                        let expected = match c_open {
+                            '{' => '}',
+                            '(' => ')',
+                            '[' => ']',
+                            '<' => '>',
+                            _ => unreachable!(),
+                        };
+                        if c != expected {
+                            skip = true;
+                            break;
+                        }
+                    } else {
+                        skip = true;
+                        break;
+                    }
+                }
+                _ => {
+                    skip = true;
+                    break;
+                }
+            }
+        }
+        if !skip {
+            scores.push(open.iter().rev().fold(0, |acc, c| {
+                acc * 5
+                    + match c {
+                        '(' => 1,
+                        '[' => 2,
+                        '{' => 3,
+                        '<' => 4,
+                        _ => unreachable!(),
+                    }
+            }));
+        }
+    }
+    scores.sort_unstable();
+    Ok(scores[scores.len() / 2])
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2021, 10).unwrap()).unwrap()).unwrap(),
+        166191
+    );
+    assert_eq!(
+        part2(parse(parse::data(2021, 10).unwrap()).unwrap()).unwrap(),
+        1152088313
+    );
+}