feat: add day4

day4/CMakeLists.txt

@@ -0,0 +1,29 @@
+cmake_minimum_required(VERSION 3.10)
+
+# Project name and version
+project(Day4 VERSION 1.0)
+
+# Set default build type
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE Debug)
+endif()
+
+# 1. This is the critical line for Clangd. 
+# It generates the file clangd reads to know where headers are.
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+# Debug and Release flags
+set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -g -O0 -Wall -Wextra")
+set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -O3")
+
+# Specify C standard
+set(CMAKE_CXX_STANDARD 23)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+# Add include directory
+include_directories(${PROJECT_SOURCE_DIR}/include)
+
+# Add executable
+add_executable(${PROJECT_NAME} 
+    src/main.cpp
+)

day4/Makefile

@@ -0,0 +1,13 @@
+
+
+clear:
+	rm -rf build/*
+
+run:
+	cp input.txt build
+	cp input_test.txt build
+	cd build && cmake .. && make && ./Day4 input_test.txt
+
+release:
+	cp input.txt build
+	cd build && cmake .. -DCMAKE_BUILD_TYPE=Release && make && ./Day4 input.txt

day4/flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1756787288,
+        "narHash": "sha256-rw/PHa1cqiePdBxhF66V7R+WAP8WekQ0mCDG4CFqT8Y=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "d0fc30899600b9b3466ddb260fd83deb486c32f1",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

day4/flake.nix

@@ -0,0 +1,58 @@
+{
+  description = "A Nix-flake-based C/C++ development environment";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs =
+    { self, nixpkgs }:
+    let
+      supportedSystems = [
+        "x86_64-linux"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+      forEachSupportedSystem =
+        f:
+        nixpkgs.lib.genAttrs supportedSystems (
+          system:
+          f {
+            pkgs = import nixpkgs { inherit system; };
+          }
+        );
+    in
+    {
+      devShells = forEachSupportedSystem (
+        { pkgs }:
+        {
+          default =
+            pkgs.mkShell.override
+              {
+                # Override stdenv in order to change compiler:
+                # stdenv = pkgs.clangStdenv;
+              }
+
+              {
+                nativeBuildInputs = with pkgs; [
+                  pkg-config
+                ];
+                packages =
+                  with pkgs;
+                  [
+                    clang-tools
+                    cmake
+                    codespell
+                    cppcheck
+                    doxygen
+                    gtest
+                    lcov
+                    nodejs
+                    vscode-extensions.vadimcn.vscode-lldb
+                  ]
+                  ++ (if system == "aarch64-darwin" then [ ] else [ gdb ]);
+                CODELLDB_PATH = "${pkgs.vscode-extensions.vadimcn.vscode-lldb}/share/vscode/extensions/vadimcn.vscode-lldb/adapter/codelldb";
+              };
+        }
+      );
+    };
+}

day4/input_test.txt

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

day4/src/main.cpp

@@ -0,0 +1,129 @@
+#include <cmath>
+#include <cstdlib>
+#include <fstream>
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+typedef std::vector<std::vector<uint8_t>> Matrix;
+
+void print_matrix(const Matrix &matrix) {
+  for (const auto &row : matrix) {
+    for (const auto &val : row) {
+      std::cout << static_cast<int>(val);
+    }
+    std::cout << std::endl;
+  }
+}
+
+int num_papers_adjacent(const Matrix &matrix, int row, int col) {
+  int element_up = 0, element_up_left = 0, element_up_right = 0,
+      element_right = 0, element_left = 0, element_down = 0,
+      element_down_left = 0, element_down_right = 0;
+  if (row > 0) {
+    element_up = matrix[row - 1][col];
+  }
+  if (row < matrix.size() - 1) {
+    element_down = matrix[row + 1][col];
+  }
+  if (col > 0) {
+    element_left = matrix[row][col - 1];
+  }
+  if (col < matrix[0].size() - 1) {
+    element_right = matrix[row][col + 1];
+  }
+
+  if (row > 0 && col > 0) {
+    element_up_left = matrix[row - 1][col - 1];
+  }
+  if (row > 0 && col < matrix[0].size() - 1) {
+    element_up_right = matrix[row - 1][col + 1];
+  }
+  if (row < matrix.size() - 1 && col > 0) {
+    element_down_left = matrix[row + 1][col - 1];
+  }
+  if (row < matrix.size() - 1 && col < matrix[0].size() - 1) {
+    element_down_right = matrix[row + 1][col + 1];
+  }
+
+  return element_up + element_up_left + element_up_right + element_right +
+         element_left + element_down + element_down_left + element_down_right;
+}
+
+int compute_accessible_papers(const Matrix &matrix) {
+  int sum = 0;
+  for (int i = 0; i < matrix.size(); i++) {
+    for (int j = 0; j < matrix[i].size(); j++) {
+      if (matrix[i][j] == 1) {
+        int num_adjacent = num_papers_adjacent(matrix, i, j);
+        sum += num_adjacent < 4 ? 1 : 0;
+      }
+    }
+  }
+  return sum;
+}
+
+int identify_and_remove_papers(Matrix &matrix, int result) {
+  std::vector<std::tuple<int, int>> to_remove;
+  for (int i = 0; i < matrix.size(); i++) {
+    for (int j = 0; j < matrix[i].size(); j++) {
+      if (matrix[i][j] == 1) {
+        int num_adjacent = num_papers_adjacent(matrix, i, j);
+        if (num_adjacent < 4) {
+          to_remove.emplace_back(i, j);
+        }
+      }
+    }
+  }
+
+  result += to_remove.size();
+  if (to_remove.size() == 0) {
+    return result;
+  }
+
+  for (const auto &t : to_remove) {
+    matrix[std::get<0>(t)][std::get<1>(t)] = 0;
+  }
+  return identify_and_remove_papers(matrix, result);
+}
+
+Matrix parse_input_file(const std::string &path) {
+  std::ifstream file;
+  std::string line;
+  Matrix matrix;
+
+  file.open(path);
+  if (file.is_open()) {
+    std::getline(file, line);
+    while (!line.empty()) {
+      std::vector<uint8_t> row(line.length(), 0);
+      for (size_t i = 0; i < line.length(); i++) {
+        if (line[i] == '@') {
+          row[i] = 1;
+        }
+      }
+      matrix.emplace_back(row);
+      std::getline(file, line);
+    }
+  } else {
+    std::cerr << "Error opening file: " << path << std::endl;
+  }
+
+  return matrix;
+}
+
+int main(int argc, char *argv[]) {
+  if (argc < 2) {
+    std::cout << "One argument required: input txt" << std::endl;
+  }
+
+  auto matrix = parse_input_file(argv[1]);
+  print_matrix(matrix);
+  int sum = compute_accessible_papers(matrix);
+  std::cout << "Number of accessible papers: " << sum << std::endl;
+
+  int removed_papers = identify_and_remove_papers(matrix, 0);
+  std::cout << "Number of removed papers: " << removed_papers << std::endl;
+
+  return 0;
+}