2024 D2P2 (I hate this)

2024/aoc.hpp

@@ -96,16 +96,24 @@ public:
 
     // Access a chunk of tokens for a given line
     // E.g. Iterate [1,2], [2,3], [3,4]
-    std::vector<std::vector<FileFragment>> ChunkView(int line, size_t n, size_t gap) {
-        std::vector<FileFragment> v = _tokens[line];
+    std::vector<std::vector<FileFragment>> ChunkView(int line, size_t size, size_t stride)
+    {
+        const auto& v = _tokens[line];
         std::vector<std::vector<FileFragment>> chunks;
-        for (size_t i = 0; i < v.size() - 1; i += gap) {
-            chunks.emplace_back(v.begin() + i,
-                                v.begin() + std::min(v.size(), i + n));
+
+        if (v.empty() || stride == 0)
+            return chunks;
+
+        for (size_t i = 0; i + size <= v.size(); i += stride)
+        {
+            std::cout << "max " << i + size << " tokens " << v.size() << " index " << i << " size " << size << " stride " << stride << std::endl;
+            chunks.emplace_back(v.begin() + i, v.begin() + i + size);
         }
+
         return chunks;
     }
 
+
     /// Iterate through all lines and their tokens
     auto begin() const { return _tokens.begin(); }
     auto end() const { return _tokens.end(); }

2024/day2.hpp

@@ -7,50 +7,80 @@ public:
     ~Day02() {}
     int Day() override {return 2;}
 
+    bool isSafe(const std::vector<int>& levels)
+    {
+        if (levels.size() < 2)
+            return true;
+
+        int dir = (levels[1] - levels[0] > 0) ? 1 : -1;
+
+        for (size_t i = 1; i < levels.size(); ++i)
+        {
+            int diff = levels[i] - levels[i - 1];
+
+            if (diff == 0)
+                return false;
+            if (std::abs(diff) > 3)
+                return false;
+            if ((diff > 0 ? 1 : -1) != dir)
+                return false;
+        }
+
+        return true;
+    }
+
+    bool isSafeWithDampener(const std::vector<int>& levels)
+    {
+        // Already safe
+        if (isSafe(levels))
+            return true;
+
+        // BRUTE FORCE
+        for (size_t i = 0; i < levels.size(); ++i)
+        {
+            std::vector<int> copy = levels;
+            copy.erase(copy.begin() + i);
+            if (isSafe(copy))
+                return true;
+        }
+
+        return false;
+    }
+
     int PartOne(File& f) override
     {
         f.SplitBy(" ");
 
-        int result_bad = 0;
+        int safe = 0;
 
-        for (int i = 0; i < f.Lines().size(); i++)
+        for (int i = 0; i < f.Lines().size(); ++i)
         {
-            bool lastDirection;
-            bool first = true;
-            for (const auto& tokenPair : f.ChunkView(i, 2, 1))
-            {
-                int token = std::atoi(tokenPair[0].Data.c_str());
-                int nextToken = std::atoi(tokenPair[1].Data.c_str());
+            std::vector<int> nums;
+            for (auto& token : f.TokensForLine(i))
+                nums.push_back(std::atoi(token.Data.c_str()));
 
-                int diff = token - nextToken;
-                bool direction = diff > 0;
-
-                if (first)
-                {
-                    lastDirection = direction;
-                    first = false;
-                }
-
-                if (std::abs(diff) > 3
-                 || token == nextToken
-                 || direction != lastDirection)
-                {
-                    result_bad++;
-                    break;
-                }
-
-                lastDirection = direction;
-                first = false;
-            }
+            if (isSafe(nums))
+                safe++;
         }
 
-        int result = f.Lines().size() - result_bad;
-
-        return result;
+        return safe;
     }
 
-    int PartTwo(File&) override
+    int PartTwo(File& f) override
     {
+        int safe = 0;
+
+        for (int i = 0; i < f.Lines().size(); ++i)
+        {
+            std::vector<int> nums;
+            for (auto& token : f.TokensForLine(i))
+                nums.push_back(std::atoi(token.Data.c_str()));
+
+            if (isSafeWithDampener(nums))
+                safe++;
+        }
+
+        return safe;
     }
 };