clean up part 2 a bit

03/main.rs

@@ -0,0 +1,94 @@
+#![allow(dead_code)]
+use std::collections::HashMap;
+use std::collections::HashSet;
+use std::fs::File;
+use std::io;
+use std::io::BufRead;
+use std::iter::FromIterator;
+use std::path::Path;
+use std::time::Instant;
+
+fn main() {
+    let now = Instant::now();
+    part_one();
+    let part_one_duration = now.elapsed();
+    part_two();
+    let part_two_duration = now.elapsed();
+    println!(
+        "p1: {}ms, p2: {}ms",
+        part_one_duration.as_millis(),
+        (part_two_duration - part_one_duration).as_millis()
+    );
+}
+
+fn read_lines<P>(filename: P) -> io::Result<io::Lines<io::BufReader<File>>>
+where
+    P: AsRef<Path>,
+{
+    // note that this discards a final newline
+    let file = File::open(filename)?;
+    Ok(io::BufReader::new(file).lines())
+}
+
+fn part_one() {
+    if let Ok(lines) = read_lines("./inputs/input") {
+        let mut priorities = 0;
+        for line in lines {
+            let mut knapsack = HashMap::<char, bool>::new();
+            if let Ok(contents) = line {
+                let pocket_one = &contents[0..contents.len() / 2];
+                let pocket_two = &contents[contents.len() / 2..];
+                for item in pocket_one.chars() {
+                    knapsack.insert(item, true);
+                }
+                for item in pocket_two.chars() {
+                    if knapsack.contains_key(&item) {
+                        if item as u32 > 96 {
+                            priorities += item as u32 - 96
+                        } else {
+                            priorities += item as u32 - 38
+                        }
+                        break;
+                    }
+                }
+            }
+        }
+        println!("{}", priorities)
+    }
+}
+
+fn part_two() {
+    if let Ok(lines) = read_lines("./inputs/input") {
+        let mut priorities = 0;
+        let mut group: Vec<HashSet<char>> = Vec::new();
+        for line in lines {
+            if let Ok(contents) = line {
+                // build the group
+                let knapsack = HashSet::from_iter(contents.chars());
+                group.push(knapsack);
+                if group.len() != 3 {
+                    continue;
+                }
+                if let (Some(one), Some(two), Some(three)) =
+                    (group.get(0), group.get(1), group.get(2))
+                {
+                    let intermediate_one: HashSet<&char> =
+                        HashSet::from_iter(two.intersection(three));
+                    let intermediate_two: HashSet<&char> =
+                        HashSet::from_iter(one.intersection(three));
+                    let mut result = intermediate_one.intersection(&intermediate_two);
+                    if let Some(item) = result.next() {
+                        // double pointers!
+                        if **item as u32 > 96 {
+                            priorities += **item as u32 - 96
+                        } else {
+                            priorities += **item as u32 - 38
+                        }
+                    }
+                }
+                group.clear();
+            }
+        }
+        println!("{}", priorities)
+    }
+}