solve day 11

2023/day11/src/faster.rs

@@ -0,0 +1,70 @@
+use std::cmp::{max, min};
+
+use helper::IteratorExt;
+
+use crate::Universe;
+
+fn height_width(universe: &Universe, count: u64) -> (Vec<u64>, Vec<u64>) {
+    let rows = universe
+        .rows
+        .iter()
+        .map(|row| if row.iter().all(|b| !b) { count } else { 1 })
+        .collect_vec();
+
+    let cols = (0..universe.rows[0].len())
+        .map(|col| {
+            if universe.rows.iter().all(|row| !row[col]) {
+                count
+            } else {
+                1
+            }
+        })
+        .collect_vec();
+
+    (rows, cols)
+}
+
+fn solve(input: &str, count: u64) -> u64 {
+    let universe = super::parse(input);
+    let (row_height, col_width) = height_width(&universe, count);
+
+    let galaxies = universe
+        .rows
+        .iter()
+        .enumerate()
+        .flat_map(|(i, row)| {
+            row.iter()
+                .copied()
+                .enumerate()
+                .filter(|&(_, b)| b)
+                .map(move |(j, _)| (i, j))
+        })
+        .collect_vec();
+
+    let mut sum = 0;
+
+    for i in 0..galaxies.len() {
+        for j in (i + 1)..galaxies.len() {
+            let lhs = galaxies[i];
+            let rhs = galaxies[j];
+
+            let x_range = min(lhs.1, rhs.1)..max(lhs.1, rhs.1);
+            let distance_x = x_range.map(|x| col_width[x]).sum::<u64>();
+
+            let y_range = min(lhs.0, rhs.0)..max(lhs.0, rhs.0);
+            let distance_y = y_range.map(|x| row_height[x]).sum::<u64>();
+
+            sum += distance_x + distance_y;
+        }
+    }
+
+    sum as u64
+}
+
+pub fn part1(input: &str) -> u64 {
+    solve(input, 2)
+}
+
+pub fn part2(input: &str) -> u64 {
+    solve(input, 1_000_000)
+}