Add 2021 solutions

2025-11-26 23:40:34 +01:00
parent ff9bd6ce01
commit 76d824471c
51 changed files with 3314 additions and 4 deletions
@@ -0,0 +1,91 @@
+#include "common/aoc.h"
+
+namespace y2021::day09
+{
+  REGISTER_DAY(2021, Day09, Array2D<int>, int);
+
+  REGISTER_TEST_EXAMPLE(2021, Day09, ExampleInput, 1, 15);
+  REGISTER_TEST(2021, Day09, Input, 1, 478);
+  REGISTER_TEST_EXAMPLE(2021, Day09, ExampleInput, 2, 1134);
+  REGISTER_TEST(2021, Day09, Input, 2, 1327014);
+
+  READ_INPUT(input)
+  {
+    return Input::ReadDigitsAsArray2D(input);
+  }
+
+  OUTPUT1(input)
+  {
+    int count = 0;
+    Index2D index{0, 0};
+    for (auto& val : input)
+    {
+      Index2D indices[4]{
+        {index.x - 1, index.y}, {index.x, index.y - 1}, {index.x + 1, index.y}, {index.x, index.y + 1}};
+      bool all = true;
+      for (auto& ind : indices)
+      {
+        if (input.IsInside(ind) && input[ind] <= val)
+        {
+          all = false;
+          break;
+        }
+      }
+      if (all)
+        count += val + 1;
+      input.Increment(index);
+    }
+    return count;
+  }
+
+  OUTPUT2(input)
+  {
+    std::vector<Index2D> basins;
+    Index2D index{0, 0};
+    for (auto& val : input)
+    {
+      Index2D indices[4]{
+        {index.x - 1, index.y}, {index.x, index.y - 1}, {index.x + 1, index.y}, {index.x, index.y + 1}};
+      bool all = true;
+      for (auto& ind : indices)
+      {
+        if (input.IsInside(ind) && input[ind] <= val)
+        {
+          all = false;
+          break;
+        }
+      }
+      if (all)
+        basins.emplace_back(index);
+      input.Increment(index);
+    }
+
+    std::vector<int> numbers;
+    for (auto&& basin : basins)
+    {
+      std::stack<Index2D> stack;
+      std::set<Index2D> visited;
+      stack.emplace(basin);
+      visited.emplace(basin);
+      while (!stack.empty())
+      {
+        auto index = stack.top();
+        stack.pop();
+        Index2D indices[4]{
+          {index.x - 1, index.y}, {index.x, index.y - 1}, {index.x + 1, index.y}, {index.x, index.y + 1}};
+        for (auto&& ind : indices)
+        {
+          if (input.IsInside(ind) && input[ind] != 9 && visited.find(ind) == visited.end())
+          {
+            stack.emplace(ind);
+            visited.emplace(ind);
+          }
+        }
+      }
+      numbers.emplace_back(visited.size());
+    }
+
+    std::sort(numbers.begin(), numbers.end());
+    return numbers[numbers.size() - 1] * numbers[numbers.size() - 2] * numbers[numbers.size() - 3];
+  }
+}