2021, day10: done

1 files changed, 65 insertions, 0 deletions

diff --git a/2021/day10/src/main.rs b/2021/day10/src/main.rs
new file mode 100644
index 0000000..dcb44a8
--- /dev/null
+++ b/2021/day10/src/main.rs
@@ -0,0 +1,65 @@
+use std::collections::HashMap;
+use std::env;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+fn main() {
+    let reader = open_file();
+    let points = HashMap::from([(')', 3), (']', 57), ('}', 1197), ('>', 25137)]);
+    let comp_points = HashMap::from([(')', 1), (']', 2), ('}', 3), ('>', 4)]);
+    let pairs = HashMap::from([('(', ')'), ('[', ']'), ('{', '}'), ('<', '>')]);
+    let opening = vec!['(', '[', '{', '<'];
+    let closing = vec![')', ']', '}', '>'];
+    let mut final_scores = Vec::new();
+
+    let mut score = 0;
+
+    for line in reader.lines() {
+        let mut stack: Vec<char> = Vec::new();
+        let mut flag = false;
+        if let Ok(ln) = line {
+            for char in ln.chars() {
+                if opening.contains(&char) {
+                    stack.push(char);
+                } else if closing.contains(&char) {
+                    let t = stack.pop().unwrap();
+                    if char == *pairs.get(&t).unwrap() {
+                    } else {
+                        score += points.get(&char).unwrap();
+                        flag = true;
+                        break;
+                    }
+                }
+            }
+            if !flag {
+                let mut score: u64 = 0;
+                stack.reverse();
+                for c in &stack {
+                    score *= 5;
+                    score += comp_points.get(pairs.get(c).unwrap()).unwrap();
+                }
+                final_scores.push(score);
+            }
+        }
+    }
+
+    final_scores.sort_unstable();
+    let idx = final_scores.len() / 2;
+
+    println!("part 1: {}", score);
+    println!("part 2: {}", final_scores[idx]);
+}
+
+fn open_file() -> BufReader<File> {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("Usage: {} <filename>", args[0]);
+        std::process::exit(1);
+    }
+
+    let filename = &args[1];
+
+    let file = File::open(filename).unwrap_or_else(|_| panic!("No such file: {}", filename));
+    BufReader::new(file)
+}