finish part 2

Author: mflinn-broad

src/days/day10.rs

@@ -1,18 +1,21 @@
+use itertools::Itertools;
+
 use crate::util;
 use std::collections::HashMap;
 
 pub fn run() {
     let raw_input = util::read_input("inputs/day10.txt").unwrap();
     let input = process(&raw_input);
 
-    println!("Part 1: {:?}", part_1(input));
+    println!("Part 1: {:?}", part_1(&input));
+    println!("Part 2: {:?}", part_2(&input));
 }
 
 fn process(input: &str) -> Vec<Vec<char>> {
     input.lines().map(|line| line.chars().collect()).collect()
 }
 
-fn part_1(input: Vec<Vec<char>>) -> usize {
+fn part_1(input: &Vec<Vec<char>>) -> usize {
     let mut error_tracker: HashMap<char, usize> = HashMap::new();
     input.iter().for_each(|line| {
         let mut stack: Vec<char> = Vec::new();
@@ -44,3 +47,71 @@ fn part_1(input: Vec<Vec<char>>) -> usize {
             _ => panic!("unreachable"),
         })
 }
+
+fn part_2(input: &Vec<Vec<char>>) -> usize {
+    // remove corrupted and complete lines
+    let completion_scores: Vec<usize> = input
+        .iter()
+        .fold(Vec::new(),|mut completions, line| {
+            let mut stack: Vec<char> = Vec::new();
+            for symbol in line {
+                match symbol {
+                    '(' => stack.push(')'),
+                    '[' => stack.push(']'),
+                    '{' => stack.push('}'),
+                    '<' => stack.push('>'),
+                    x if *x == stack[stack.len() - 1] => {
+                        stack.pop();
+                    }
+                    _ => {
+                        return completions;
+                    }
+                }
+            }
+            if stack.len() == 0 {
+                completions
+            } else {
+                completions.push(stack);
+                completions
+            }
+        })
+        .iter()
+        .map(|completion| {
+            completion.iter().rev().fold(0, |score, symbol| match symbol {
+                ')' => (score * 5) + 1,
+                ']' => (score * 5) + 2,
+                '}' => (score * 5) + 3,
+                '>' => (score * 5) + 4,
+                _ => panic!("unreachable"),
+            })
+        })
+        .sorted()
+        .collect();
+
+    completion_scores[completion_scores.len() / 2]
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    extern crate test;
+    use test::Bencher;
+
+    #[bench]
+    fn bench_part_1(b: &mut Bencher) {
+        let raw_input = util::read_input("inputs/day10.txt").unwrap();
+        b.iter(|| {
+            let mut input = process(&raw_input);
+            part_1(&mut input);
+        });
+    }
+
+    #[bench]
+    fn bench_part_2(b: &mut Bencher) {
+        let raw_input = util::read_input("inputs/day10.txt").unwrap();
+        b.iter(|| {
+            let input = process(&raw_input);
+            part_2(&input);
+        });
+    }
+}