Day 3

diff --git a/data/day03.input b/data/day03.input
new file mode 100644 (file)
index 0000000..cb4dee4
--- /dev/null
+++ b/data/day03.input
@@ -0,0 +1,300 @@
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diff --git a/src/day03.rs b/src/day03.rs
index fb593c2..a15f11b 100644 (file)
--- a/src/day03.rs
+++ b/src/day03.rs
@@ -1,18 +1,61 @@
-use std::io::BufRead;
+use std::io::{BufRead, Lines};
 
-pub fn read_<R>(reader: R) -> Vec<i32>
+use itertools::Itertools;
+
+pub fn priority_sum<R>(reader: R) -> i32
 where
     R: BufRead
 {
-    /*
-    let mut shapes: Vec<(Shape, Shape)> = Vec::new();
+    let mut sum = 0;
+    let mut item_count = [0i32; 52];
     for l in reader.lines() {
-        let s: Vec<Shape> = l.unwrap().trim().split(' ').map(Shape::parse).collect();
-        shapes.push((s[0], s[1]));
+        item_count.fill(0);
+        let l = l.unwrap();
+        let items = l.as_bytes();
+        for i in 0..items.len() / 2 {
+            let v = letter_to_priority(items[i]);
+            item_count[v as usize - 1] += 1;
+        }
+        for i in items.len() / 2..items.len() {
+            let v = letter_to_priority(items[i]);
+            if item_count[v as usize - 1] > 0 {
+                sum += v as i32;
+                break;
+            }
+        }
+    }
+    sum
+}
+
+pub fn badge_sum<R>(reader: R) -> i32
+where
+    R: BufRead
+{
+    let mut sum = 0;
+    let mut item_count = [0i32; 52];
+    for group in reader.lines().chunks(3).into_iter() {
+        item_count.fill(0);
+        for (i, rucksack) in group.enumerate() {
+            let items = rucksack.unwrap();
+            for b in items.as_bytes().into_iter() {
+                let v = letter_to_priority(*b);
+                if i == 2 && item_count[v as usize - 1] == 3 {
+                    sum += v as i32;
+                    break;
+                }
+                item_count[v as usize - 1] |= 1 << i;
+            }
+        }
+    }
+    sum
+}
+
+fn letter_to_priority(v: u8) -> u8 {
+    if v >= 97 { // >= 'a'
+        v - 96
+    } else { // < 'a'
+        v - 38
     }
-    shapes
-     */
-    Vec::new()
 }
 
 #[cfg(test)]
@@ -21,11 +64,27 @@ mod tests {
 
     #[test]
     fn part1() {
-        assert_eq!(1, 1);
+        let rucksacks =
+        "vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw";
+
+        assert_eq!(priority_sum(rucksacks.as_bytes()), 157);
     }
 
     #[test]
     fn part2() {
-        assert_eq!(2, 2);
+        let rucksacks =
+        "vJrwpWtwJgWrhcsFMMfFFhFp
+jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
+PmmdzqPrVvPwwTWBwg
+wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
+ttgJtRGJQctTZtZT
+CrZsJsPPZsGzwwsLwLmpwMDw";
+
+        assert_eq!(badge_sum(rucksacks.as_bytes()), 70);
     }
 }
\ No newline at end of file

diff --git a/src/main.rs b/src/main.rs
index 6a78796..66d8ef0 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -20,7 +20,11 @@ fn day02() -> String {
 }
 
 fn day03() -> String {
-    format!("part1: {}, part2: {}", 0, 0)
+    let mut f = fs::File::open("data/day03.input").unwrap();
+    let part1 = day03::priority_sum(BufReader::new(f.try_clone().unwrap()));
+    let _ = f.seek(SeekFrom::Start(0));
+    let part2 = day03::badge_sum(BufReader::new(f));
+    format!("part1: {}, part2: {}", part1, part2)
 }
 
 fn format_micros(t: u128) -> String {