2018 day 3

Author: ictrobot

crates/year2018/src/day03.rs

@@ -0,0 +1,92 @@
+use utils::prelude::*;
+
+/// Identifying the region that isn't overlapped.
+#[derive(Clone, Debug)]
+pub struct Day03 {
+    part1: u32,
+    part2: u32,
+}
+
+#[derive(Debug)]
+struct Claim {
+    id: u32,
+    y: usize,
+    height: usize,
+    idx: usize,
+    mask0: u32,
+    mask1: u32,
+}
+
+impl Day03 {
+    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
+        let coordinate = parser::number_range(0usize..=991);
+        let dimension = parser::number_range(1usize..=31);
+
+        let claims: Vec<Claim> = parser::u32()
+            .with_prefix(b'#')
+            .with_suffix(" @ ")
+            .then(coordinate.with_suffix(b','))
+            .then(coordinate.with_suffix(": "))
+            .then(dimension.with_suffix(b'x'))
+            .then(dimension)
+            .map_res(|(id, x, y, width, height)| {
+                if x + width > 1000 || y + height > 1000 {
+                    Err("claim out of bounds")
+                } else {
+                    let mask = ((1u64 << width) - 1) << (x % 32);
+
+                    Ok(Claim {
+                        id,
+                        y,
+                        height,
+                        idx: (x / 32),
+                        mask0: mask as u32,
+                        mask1: (mask >> 32) as u32,
+                    })
+                }
+            })
+            .parse_lines(input)?;
+
+        let mut grid = [[0u32; 32]; 1000];
+        let mut overlaps = [[0u32; 32]; 1000];
+        for claim in &claims {
+            // This is enforced by the max accepted coordinate. 991 div 32 = 30
+            assert!(claim.idx + 1 < 32);
+
+            for y in claim.y..claim.y + claim.height {
+                overlaps[y][claim.idx] |= grid[y][claim.idx] & claim.mask0;
+                grid[y][claim.idx] |= claim.mask0;
+
+                overlaps[y][claim.idx + 1] |= grid[y][claim.idx + 1] & claim.mask1;
+                grid[y][claim.idx + 1] |= claim.mask1;
+            }
+        }
+
+        Ok(Self {
+            part1: overlaps.as_flattened().iter().map(|x| x.count_ones()).sum(),
+            part2: claims
+                .iter()
+                .find(|claim| {
+                    overlaps[claim.y..claim.y + claim.height].iter().all(|o| {
+                        o[claim.idx] & claim.mask0 == 0 && o[claim.idx + 1] & claim.mask1 == 0
+                    })
+                })
+                .ok_or_else(|| InputError::new(input, 0, "all claims overlap"))?
+                .id,
+        })
+    }
+
+    #[must_use]
+    pub fn part1(&self) -> u32 {
+        self.part1
+    }
+
+    #[must_use]
+    pub fn part2(&self) -> u32 {
+        self.part2
+    }
+}
+
+examples!(Day03 -> (u32, u32) [
+    {input: "#1 @ 1,3: 4x4\n#2 @ 3,1: 4x4\n#3 @ 5,5: 2x2", part1: 4},
+]);

crates/year2018/src/lib.rs

@@ -4,4 +4,5 @@
 utils::year!(2018 => year2018, ${
     1 => day01::Day01,
     2 => day02::Day02,
+    3 => day03::Day03,
 });