Day 11 done.

input/day11.txt

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src/day11.rs

@@ -0,0 +1,48 @@
+use std::io;
+
+pub fn sum_pairs(universe: &Vec<Vec<char>>, ratio: u64) -> u64 {
+  let mut empty_columns: Vec<bool> = vec![true; universe[0].len()];
+  let mut empty_rows: Vec<bool> = vec![true; universe.len()];
+
+  let mut galaxies: Vec<(usize, usize)> = Vec::new();
+  for r in 0..universe.len() {
+    for c in 0..universe[r].len() {
+      if universe[r][c] == '#' {
+        empty_rows[r] = false;
+        empty_columns[c] = false;
+        galaxies.push((r, c));
+      }
+    }
+  }
+
+  let mut sum: u64 = 0;
+  for i in 0..galaxies.len() {
+    let (r1, c1) = galaxies[i];
+    for j in (i + 1)..galaxies.len() {
+      let (r2, c2) = galaxies[j];
+      let rmin = r1.min(r2);
+      let rmax = r1.max(r2);
+      let cmin = c1.min(c2);
+      let cmax = c1.max(c2);
+
+      let cartdistance = ((rmax - rmin) + (cmax - cmin)) as u64;
+      let addcols = empty_columns[cmin..=cmax].iter().filter(|b| **b).count() as u64;
+      let addrows = empty_rows[rmin..=rmax].iter().filter(|b| **b).count() as u64;
+      sum += cartdistance + (addcols * ratio) + (addrows * ratio);
+    }
+  }
+
+  sum
+}
+
+pub fn sum_lengths(ratio: u64) -> u64 {
+  let mut buffer = String::new();
+
+  let mut universe: Vec<Vec<char>> = Vec::new();
+  while io::stdin().read_line(&mut buffer).unwrap() > 0 {
+    universe.push(buffer.trim().chars().collect());
+    buffer = String::new();
+  }
+
+  sum_pairs(&universe, ratio)
+}

src/main.rs

@@ -2,6 +2,7 @@ use std::env;
 
 mod day1;
 mod day10;
+mod day11;
 mod day2;
 mod day3;
 mod day4;
@@ -38,6 +39,8 @@ fn main() {
     "day9b" => println!("Sum: {}", day9::sum_next(true)),
     "day10a" => println!("Steps: {}", day10::num_steps().0),
     "day10b" => println!("Contains: {}", day10::num_steps().1),
+    "day11a" => println!("Sum: {}", day11::sum_lengths(1)),
+    "day11b" => println!("Sum: {}", day11::sum_lengths(999999)),
     _ => println!("Unrecognized day: {}", args[1]),
   }
 }