From 98d927cd72b5c5209c4a0516657598f3698f4f33 Mon Sep 17 00:00:00 2001
From: Joshua Smallwood <31932412+smallwoj@users.noreply.github.com>
Date: Thu, 4 Dec 2025 07:54:45 -0600
Subject: [PATCH] feat: solve day 4

---
 data/examples/04.txt |  11 ++++
 src/bin/04.rs        | 143 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 154 insertions(+)
 create mode 100644 data/examples/04.txt
 create mode 100644 src/bin/04.rs

diff --git a/data/examples/04.txt b/data/examples/04.txt
new file mode 100644
index 0000000..ad7791d
--- /dev/null
+++ b/data/examples/04.txt
@@ -0,0 +1,11 @@
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.
+
diff --git a/src/bin/04.rs b/src/bin/04.rs
new file mode 100644
index 0000000..73cd87a
--- /dev/null
+++ b/src/bin/04.rs
@@ -0,0 +1,143 @@
+advent_of_code::solution!(4);
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let char_grid: Vec<Vec<char>> = input
+        .split('\n')
+        .filter(|el| !el.is_empty())
+        .map(|line| line.chars().collect())
+        .collect();
+    let mut num_rolls = 0;
+    for (i, row) in char_grid.iter().enumerate() {
+        for (j, c) in row.iter().enumerate() {
+            let mut num = 0;
+            if *c == '@' {
+                if (i + 1) < char_grid.len() && char_grid[i + 1][j] == '@' {
+                    num += 1;
+                }
+
+                if (i + 1) < char_grid.len()
+                    && (j + 1) < row.len()
+                    && char_grid[i + 1][j + 1] == '@'
+                {
+                    num += 1;
+                }
+
+                if (j + 1) < row.len() && char_grid[i][j + 1] == '@' {
+                    num += 1;
+                }
+
+                if (i as i32 - 1) >= 0 && (j + 1) < row.len() && char_grid[i - 1][j + 1] == '@' {
+                    num += 1;
+                }
+
+                if (i as i32 - 1) as i32 >= 0 && char_grid[i - 1][j] == '@' {
+                    num += 1;
+                }
+
+                if (i as i32 - 1) as i32 >= 0
+                    && (j as i32 - 1) >= 0
+                    && char_grid[i - 1][j - 1] == '@'
+                {
+                    num += 1;
+                }
+
+                if (j as i32 - 1) >= 0 && char_grid[i][j - 1] == '@' {
+                    num += 1;
+                }
+
+                if i + 1 < char_grid.len() && (j as i32 - 1) >= 0 && char_grid[i + 1][j - 1] == '@'
+                {
+                    num += 1;
+                }
+                if num < 4 {
+                    num_rolls += 1;
+                }
+            }
+        }
+    }
+    Some(num_rolls)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let mut char_grid: Vec<Vec<char>> = input
+        .split('\n')
+        .filter(|el| !el.is_empty())
+        .map(|line| line.chars().collect())
+        .collect();
+    let mut num_rolls = 0;
+    let mut done = false;
+    while !done {
+        done = true;
+        for (i, row) in char_grid.clone().iter().enumerate() {
+            for (j, c) in row.clone().iter().enumerate() {
+                let mut num = 0;
+                if *c == '@' {
+                    if (i + 1) < char_grid.len() && char_grid[i + 1][j] == '@' {
+                        num += 1;
+                    }
+
+                    if (i + 1) < char_grid.len()
+                        && (j + 1) < row.len()
+                        && char_grid[i + 1][j + 1] == '@'
+                    {
+                        num += 1;
+                    }
+
+                    if (j + 1) < row.len() && char_grid[i][j + 1] == '@' {
+                        num += 1;
+                    }
+
+                    if (i as i32 - 1) >= 0 && (j + 1) < row.len() && char_grid[i - 1][j + 1] == '@'
+                    {
+                        num += 1;
+                    }
+
+                    if (i as i32 - 1) as i32 >= 0 && char_grid[i - 1][j] == '@' {
+                        num += 1;
+                    }
+
+                    if (i as i32 - 1) as i32 >= 0
+                        && (j as i32 - 1) >= 0
+                        && char_grid[i - 1][j - 1] == '@'
+                    {
+                        num += 1;
+                    }
+
+                    if (j as i32 - 1) >= 0 && char_grid[i][j - 1] == '@' {
+                        num += 1;
+                    }
+
+                    if i + 1 < char_grid.len()
+                        && (j as i32 - 1) >= 0
+                        && char_grid[i + 1][j - 1] == '@'
+                    {
+                        num += 1;
+                    }
+                    if num < 4 {
+                        num_rolls += 1;
+                        char_grid[i][j] = '.';
+                        done = false;
+                    }
+                }
+            }
+        }
+    }
+    Some(num_rolls)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(13));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(43));
+    }
+}