From 60e78353d7ef3e70b255d6a01a77adf5e8f08981 Mon Sep 17 00:00:00 2001
From: mnerv <24420859+mnerv@users.noreply.github.com>
Date: Sun, 14 Dec 2025 12:43:52 +0100
Subject: [PATCH] 2025 day 4 p1

---
 2025/CMakeLists.txt |  1 +
 2025/day04.cpp      | 83 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 2025/day04.cpp

diff --git a/2025/CMakeLists.txt b/2025/CMakeLists.txt
index 4fd1213..7626e6e 100644
--- a/2025/CMakeLists.txt
+++ b/2025/CMakeLists.txt
@@ -31,4 +31,5 @@ add_day_executables(
     "day01.cpp"
     "day02.cpp"
     "day03.cpp"
+    "day04.cpp"
 )
diff --git a/2025/day04.cpp b/2025/day04.cpp
new file mode 100644
index 0000000..9eb20fa
--- /dev/null
+++ b/2025/day04.cpp
@@ -0,0 +1,83 @@
+#include <span>
+#include <algorithm>
+#include <ranges>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+#include "fmt/std.h"
+
+#include "aoc/types.hpp"
+#include "aoc/utils.hpp"
+
+using namespace std::string_view_literals;
+using namespace aoc::types;
+
+// starts at 50
+[[maybe_unused]]constexpr auto raw_str = R"(
+..@@.@@@@.
+@@@.@.@.@@
+@@@@@.@.@@
+@.@@@@..@.
+@@.@@@@.@@
+.@@@@@@@.@
+.@.@.@.@@@
+@.@@@.@@@@
+.@@@@@@@@.
+@.@.@@@.@.
+)";
+
+static auto entry([[maybe_unused]]std::span<char const*> const& args) -> void {
+    // std::string str{raw_str};
+    auto str = aoc::read_text("./input.txt").value_or("");
+    str = aoc::trim(str);
+
+    fmt::print("INPUT\n");
+    fmt::print("⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼⎽⎼⎻⎺⎻⎼\n");
+    fmt::print("{}\n", str);
+    fmt::print("{}\n", std::string(80, '-'));
+
+    auto grid = str | std::views::split("\n"sv) | std::views::transform([](auto const& str) {
+        return aoc::trim(std::string{std::begin(str), std::end(str)}) |
+            std::views::transform([](auto const& ch) { return ch; }) |
+            std::ranges::to<std::vector>();
+    }) | std::ranges::to<std::vector>();
+
+    u64 access = 0;
+    for (isize i = 0; i < isize(grid.size()); ++i) {
+        for (isize j = 0; j < isize(grid[i].size()); ++j) {
+            auto const v = grid[i][j];
+            if (v == '.') continue;
+
+            u64 sum = 0;
+            if (i - 1 >= 0 && j - 1 >= 0 && grid[i - 1][j - 1] == '@') ++sum;
+            if (i - 1 >= 0 && grid[i - 1][j] == '@') ++sum;
+            if (i - 1 >= 0 && j + 1 < isize(grid[i].size()) && grid[i - 1][j + 1] == '@') ++sum;
+
+            if (j - 1 >= 0 && grid[i][j - 1] == '@') ++sum;
+            if (j + 1 < isize(grid[i].size()) && grid[i][j + 1] == '@') ++sum;
+
+            if (i + 1 < isize(grid.size()) && j - 1 >= 0 && grid[i + 1][j - 1] == '@') ++sum;
+            if (i + 1 < isize(grid.size()) && grid[i + 1][j] == '@') ++sum;
+            if (i + 1 < isize(grid.size()) && j + 1 < isize(grid[i].size()) && grid[i + 1][j + 1] == '@') ++sum;
+
+            if (sum < 4) {
+                // fmt::print("{},{}: {}\n", i, j, sum);
+                ++access;
+            }
+        }
+    }
+
+    fmt::print("res: {}\n", access);
+}
+
+auto main([[maybe_unused]]int argc, [[maybe_unused]]char const* argv[]) -> int {
+    try {
+        entry({argv, std::next(argv, argc)});
+    } catch (std::exception const& e) {
+        fmt::print(stderr, "{}\n", e.what());
+        return 1;
+    }
+    return 0;
+}