2025 Day 12 (Thanks for the input Eric - Merry Christmas)

Author: hsaikia

src/bin/2025_12/main.rs

@@ -0,0 +1,70 @@
+use aoc::{common, grid::Grid, io};
+
+fn solve<const PART: usize>(input: &str) -> usize {
+    let mut ans = 0;
+
+    let mut shape_lines = Vec::new();
+    let mut cases: Vec<(usize, usize, Vec<usize>)> = Vec::new();
+    for line in input.lines() {
+        if line.is_empty() {
+            continue;
+        }
+        if line.contains("x") {
+            if let Some((dim, vals)) = line.split_once(": ") {
+                let dims = io::tokenize_nums(dim, "x");
+                let values = io::tokenize_nums(vals, " ");
+                cases.push((dims[0], dims[1], values));
+            }
+        } else {
+            shape_lines.push(line);
+        }
+    }
+
+    let total_shapes = shape_lines.iter().filter(|l| l.contains(":")).count();
+    let mut shapes: Vec<Grid<char>> = vec![Grid::new(3, 3, '.'); total_shapes];
+
+    for i in 0..total_shapes {
+        for r in 0..3 {
+            shapes[i].set_row(r, shape_lines[4 * i + r + 1].chars().collect());
+        }
+    }
+
+    // LEt's figure out the clear YESes and clear NOs first..
+    // Clear yes : Can fit all 3x3 shapes
+    // Clear no : Total space too little to fit even all solid spaces
+
+    let solid_spaces: Vec<usize> = shapes.iter().map(|g| g.count(&'#')).collect();
+
+    for (d0, d1, number) in &cases {
+        let x = d0 / 3;
+        let y = d1 / 3;
+        let n = number.iter().sum();
+        if x * y >= n {
+            println!("Trivial YES");
+            ans += 1;
+            continue;
+        }
+
+        let min_solid_spaces_required: usize = number
+            .iter()
+            .zip(solid_spaces.iter())
+            .map(|(x, y)| x * y)
+            .sum();
+
+        if min_solid_spaces_required > d0 * d1 {
+            println!("Trivial NO");
+            continue;
+        }
+
+        // Thanks for the input Eric!
+        println!("Tough : {}x{} : {:?}", d0, d1, number);
+    }
+
+    ans
+}
+
+fn main() {
+    if let Some(input) = common::get_input() {
+        common::timed(&input, solve::<1>, true);
+    }
+}