day4 part1

Author: daanbreur

rust2025/src/days/d04.rs

@@ -1,29 +1,74 @@
+use crate::dprintln;
+
 use super::{Answer, Day, DayImpl};
 
 const CURRENT_DAY: u8 = 4;
 
-type Data = Vec<u64>;
+type Data = Vec<Vec<bool>>;
 impl DayImpl<Data> for Day<CURRENT_DAY> {
     fn init_test() -> (Self, Data) {
         Self::init(include_str!("test_inputs/test04.txt"))
     }
 
     fn expected_results() -> (Answer, Answer) {
-        (Answer::Number(0), Answer::Number(0))
+        (Answer::Number(13), Answer::Number(0))
     }
 
     fn init(input: &str) -> (Self, Data) {
         (
             Self {},
             input
                 .lines()
-                .map(|v| v.parse::<u64>().expect("error while parsing input."))
+                .map(|line| {
+                    line.chars()
+                        .map(|c| match c {
+                            '@' => true,
+                            '.' => false,
+                            _ => panic!("Unexpected character in input"),
+                        })
+                        .collect()
+                })
                 .collect(),
         )
     }
 
     fn one(&self, data: &mut Data) -> Answer {
-        Answer::Number(data.len() as u64)
+        dprintln!("input data: {:?}", data);
+
+        let mut count: u64 = 0;
+
+        let (w, h) = (data[0].len(), data.len());
+
+        for i in 0..h {
+            for j in 0..w {
+                if !data[i][j] { continue; }
+
+                let mut neighbors = 0;
+
+                for di in -1..=1 {
+                    for dj in -1..=1 {
+                        if di == 0 && dj == 0 { continue; }
+
+                        let neighbor_i = i as isize + di;
+                        let neighbor_j = j as isize + dj;
+
+                        if neighbor_i < 0 || neighbor_i >= h as isize || neighbor_j < 0 || neighbor_j >= w as isize {
+                            continue;
+                        }
+
+                        if data[neighbor_i as usize][neighbor_j as usize] {
+                            neighbors += 1;
+                        }
+                    }
+                }
+
+                if neighbors < 4 {
+                    count += 1;
+                }
+            }
+        }
+        
+        Answer::Number(count)
     }
 
     fn two(&self, data: &mut Data) -> Answer {

rust2025/src/days/test_inputs/test04.txt

@@ -0,0 +1,10 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.