Add solution for 2025 Day 4

res/2025/day04/test_input.txt

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

src/2025/Day04.cpp

@@ -2,35 +2,62 @@
 
 namespace y2025::day04
 {
-  using InputType = std::vector<int>;
+  using InputType = Array2D<char>;
   REGISTER_DAY(2025, Day04, InputType, int);
 
-  REGISTER_TEST_EXAMPLE(2025, Day04, ExampleInput, 1, 0);
-  REGISTER_TEST(2025, Day04, Input, 1, 0);
-  REGISTER_TEST_EXAMPLE(2025, Day04, ExampleInput, 2, 0);
-  REGISTER_TEST(2025, Day04, Input, 2, 0);
+  REGISTER_TEST_EXAMPLE(2025, Day04, ExampleInput, 1, 13);
+  REGISTER_TEST(2025, Day04, Input, 1, 1502);
+  REGISTER_TEST_EXAMPLE(2025, Day04, ExampleInput, 2, 43);
+  REGISTER_TEST(2025, Day04, Input, 2, 9083);
 
   READ_INPUT(input)
   {
-    std::vector<int> vec;
-    std::string str;
-    while (std::getline(input, str))
-    {
-      std::stringstream ss{str};
-      int n;
-      ss >> n;
-      vec.emplace_back(n);
-    }
-    return vec;
+    return Input::ReadArray2D(input);
   }
 
   OUTPUT1(input)
   {
-    return 0;
+    std::set<Index2D> toiletPapers;
+    for (auto it = input.begin(); it != input.end(); it++)
+    {
+      if (input[it.index] != '@' || input.GetNeighbors('@', it.index.x, it.index.y, 1) >= 4)
+        continue;
+
+      toiletPapers.emplace(it.index);
+    }
+    return toiletPapers.size();
   }
 
   OUTPUT2(input)
   {
-    return 0;
+    Array2D<char> cpy = input;
+
+    std::stack<Index2D> toCheck;
+    for (auto it = cpy.begin(); it != cpy.end(); it++)
+    {
+      if (cpy[it.index] == '.' || cpy.GetNeighbors('@', it.index.x, it.index.y, 1) >= 4)
+        continue;
+
+      toCheck.emplace(it.index);
+    }
+
+    int removedToiletPapers = 0;
+    while (!toCheck.empty())
+    {
+      Index2D top = toCheck.top();
+      toCheck.pop();
+      if (cpy[top] == '.' || cpy.GetNeighbors('@', top.x, top.y, 1) >= 4)
+        continue;
+
+      cpy[top] = '.';
+      removedToiletPapers++;
+      std::vector<Index2D> neighbors = cpy.GetNeighbors(top, true);
+      for (auto neighbor : neighbors)
+      {
+        if (cpy[neighbor] == '@')
+          toCheck.emplace(neighbor);
+      }
+    }
+    return removedToiletPapers;
   }
 }