Day 20

src/Days/D20.c

@@ -0,0 +1,305 @@
+#include <stddef.h>
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#define max(a,b)             \
+({                           \
+    __typeof__ (a) _a = (a); \
+    __typeof__ (b) _b = (b); \
+    _a > _b ? _a : _b;       \
+})
+
+///////////////////
+// AVL-TREE NODE //
+///////////////////
+
+typedef struct Node {
+  struct Node *parent;
+  struct Node *leftChild;
+  struct Node *rightChild;
+  int32_t size;
+  int32_t height;
+  int64_t value;
+} Node;
+
+////////////////////////////////
+// NULL-SAFE NODE DATA ACCESS //
+////////////////////////////////
+
+int32_t height(Node *node)
+{
+  return node == NULL ? 0 : node->height;
+}
+
+int32_t size(Node *node)
+{
+  return node == NULL ? 0 : node->size;
+}
+
+int balance(Node *node)
+{
+  return node == NULL ? 0 : height(node->leftChild) - height(node->rightChild);
+}
+
+
+///////////
+// RESET //
+///////////
+
+void resetHeight(Node *node)
+{
+  node->height = 1 + max(height(node->leftChild), height(node->rightChild));
+}
+
+void resetSize(Node *node)
+{
+  node->size = 1 + size(node->leftChild) + size(node->rightChild);
+}
+
+
+///////////////////
+// AVL-ROTATIONS //
+///////////////////
+
+Node *rotateL(Node *root)
+{
+  assert(root);
+  assert(root->rightChild);
+
+  Node *newRoot = root->rightChild;
+  Node *transfer = newRoot->leftChild;
+
+  newRoot->leftChild = root;
+  root->rightChild = transfer;
+
+  newRoot->parent = root->parent;
+  root->parent = newRoot;
+
+  if (transfer != NULL) transfer->parent = root;
+
+  resetSize(root);
+  resetSize(newRoot);
+
+  resetHeight(root);
+  resetHeight(newRoot);
+
+  return newRoot;
+}
+
+Node *rotateR(Node *root)
+{
+  assert(root);
+  assert(root->leftChild);
+
+  Node *newRoot = root->leftChild;
+  Node *transfer = newRoot->rightChild;
+
+  newRoot->rightChild = root;
+  root->leftChild = transfer;
+
+  newRoot->parent = root->parent;
+  root->parent = newRoot;
+
+  if (transfer != NULL) transfer->parent = root;
+
+  resetSize(root);
+  resetSize(newRoot);
+
+  resetHeight(root);
+  resetHeight(newRoot);
+
+  return newRoot;
+}
+
+///////////////////
+// MODIFICATIONS //
+///////////////////
+
+Node *insert_pos_rec(Node *root, int pos, Node *newNode, Node *parent)
+{
+    assert(0 <= pos && (!root || pos <= root->size));
+
+    if (root == NULL) {
+        assert(pos == 0);
+
+        newNode->leftChild = NULL;
+        newNode->rightChild = NULL;
+        if (parent != NULL) newNode->parent = parent;
+
+        resetSize(newNode);
+        resetHeight(newNode);
+
+        return newNode;
+    }
+
+    if (pos <= size(root->leftChild))
+        root->leftChild = insert_pos_rec(root->leftChild, pos, newNode, root);
+    else
+        root->rightChild = insert_pos_rec(root->rightChild, pos - size(root->leftChild) - 1,
+                                             newNode, root);
+
+    resetSize(root);
+    resetHeight(root);
+
+    int bal = balance(root);
+
+    if (bal > 1) {
+        if (pos > size(root->leftChild->leftChild))
+            root->leftChild = rotateL(root->leftChild);
+
+        root = rotateR(root);
+    }
+
+    if (bal < -1) {
+        int posUpd = pos - size(root->leftChild) - 1;
+
+        if (posUpd <= size(root->rightChild->leftChild))
+            root->rightChild = rotateR(root->rightChild);
+
+        root = rotateL(root);
+    }
+
+    return root;
+}
+
+Node *insert_pos(Node *root, int pos, Node *newNode)
+{
+    return insert_pos_rec(root, pos, newNode, NULL);
+}
+
+Node *delete_pos_rec(Node *root, int pos, Node **victim)
+{
+    assert(root);
+    assert(0 <= pos && (!root || pos <= root->size));
+
+    if (pos < size(root->leftChild))
+        root->leftChild = delete_pos_rec(root->leftChild, pos, victim);
+    else if (pos > size(root->leftChild))
+        root->rightChild = delete_pos_rec(root->rightChild, pos - size(root->leftChild) - 1, victim);
+    else {
+        *victim = root;
+
+        if (root->leftChild == NULL) return root->rightChild;
+        if (root->rightChild == NULL) return root->leftChild;
+
+        Node *replacement;
+        root->rightChild = delete_pos_rec(root->rightChild, 0, &replacement);
+
+        replacement->leftChild = root->leftChild;
+        replacement->rightChild = root->rightChild;
+        replacement->parent = root->parent;
+
+        root = replacement;
+    }
+
+    if (root->leftChild) root->leftChild->parent = root;
+    if (root->rightChild) root->rightChild->parent = root;
+
+    resetSize(root);
+    resetHeight(root);
+
+    int bal = balance(root);
+
+    if (bal > 1) {
+        if (balance(root->leftChild) < 0)
+            root->leftChild = rotateL(root->leftChild);
+
+        root = rotateR(root);
+    }
+
+    if (bal < -1) {
+        if (balance(root->rightChild) > 0)
+            root->rightChild = rotateR(root->rightChild);
+
+        root = rotateL(root);
+    }
+
+    return root;
+}
+
+Node *delete_pos(Node *root, int pos, Node **victim)
+{
+    return delete_pos_rec(root, pos, victim);
+}
+
+int wrap(long long n, int mod)
+{
+    return (n % mod + mod) % mod;
+}
+
+//////////////
+// QUERYING //
+//////////////
+
+Node *node_at_position(Node *root, int pos)
+{
+  assert(root);
+  assert(0 <= pos && pos <= root->size);
+
+  if (pos < size(root->leftChild))
+	return node_at_position(root->leftChild, pos);
+  else if (pos > size(root->leftChild))
+	return node_at_position(root->rightChild, pos - size(root->leftChild) - 1);
+  else
+	return root;
+}
+
+int32_t position_of_node(Node *node) {
+    int32_t pos = size(node->leftChild);
+
+    for (; node->parent; node = node->parent)
+        if (node->parent->rightChild == node)
+            pos += size(node->parent->leftChild) + 1;
+
+    return pos;
+}
+
+/////////////
+// FFI API //
+/////////////
+
+typedef struct CyclicList {
+  Node *root;
+  Node *nodes;
+} CyclicList;
+
+int32_t position_of_nth_value(CyclicList *cl, int32_t n) {
+  assert(0 <= n && n < cl->root->size);
+  return position_of_node(&cl->nodes[n]);
+}
+
+int64_t value_at_position(CyclicList *cl, int32_t pos) {
+  return node_at_position(cl->root, wrap(pos, cl->root->size))->value;
+}
+
+CyclicList *cyclic_list_from_array(int64_t *values, int numValues) {
+  CyclicList* cl = malloc(sizeof(CyclicList));
+
+  cl->root = NULL;
+  cl->nodes = (Node *) malloc(sizeof(Node) * numValues);
+
+  for (int i = 0; i < numValues; i++)
+	cl->nodes[i].value = values[i];
+
+  for (int i = 0; i < numValues; i++)
+	cl->root = insert_pos(cl->root, i, &cl->nodes[i]);
+
+  return cl;
+}
+
+void mix(CyclicList *cl, int32_t rounds) {
+    Node *victim;
+
+	int length = cl->root->size;
+    for (int j = 0; j < rounds; j++) {
+        for (int i = 0; i < length; i++) {
+            int idx = position_of_node(&cl->nodes[i]);
+            cl->root = delete_pos(cl->root, idx, &victim);
+            int newIdx = wrap(idx + victim->value, length - 1);
+            cl->root = insert_pos(cl->root, newIdx, victim);
+        }
+    }
+}

src/Days/D20.hs

@@ -0,0 +1,69 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+
+module Days.D20 where
+
+import Common
+import Data.Int (Int32, Int64)
+import Data.Maybe (fromJust)
+import Data.Vector.Storable qualified as Vector
+import Foreign qualified
+import Parse
+import System.IO.Unsafe (unsafePerformIO)
+
+-- Dummy types for FFI
+data CyclicList = CyclicList
+
+foreign import ccall unsafe "cyclic_list_from_array"
+  cMkCyclicList ::
+    Foreign.Ptr Int64 ->
+    Int32 ->
+    Foreign.Ptr CyclicList
+
+foreign import ccall unsafe "mix"
+  cMix ::
+    Foreign.Ptr CyclicList ->
+    Int32 ->
+    IO ()
+
+foreign import ccall unsafe "position_of_nth_value"
+  cPositionOfNthValue ::
+    Foreign.Ptr CyclicList ->
+    Int32 ->
+    Int32
+
+foreign import ccall unsafe "value_at_position"
+  cValueAtPosition ::
+    Foreign.Ptr CyclicList ->
+    Int32 ->
+    Int64
+
+parser :: Parser [Int]
+parser = someLines int
+
+decrypt :: Int -> [Int] -> [Int64]
+decrypt rounds numbers =
+  let iv = Vector.fromList $ map (fromIntegral :: Int -> Int64) numbers
+      zeroIndex = fromJust $ Vector.elemIndex 0 iv
+      (dataPtr, dataLen) = Vector.unsafeToForeignPtr0 iv
+      groveOffsets = [1000, 2000, 3000]
+   in unsafePerformIO $
+        Foreign.withForeignPtr
+          dataPtr
+          ( \ptr -> do
+              let cycList = cMkCyclicList ptr (fromIntegral dataLen)
+              cMix cycList (fromIntegral rounds)
+              let zeroPos = cPositionOfNthValue cycList (fromIntegral zeroIndex)
+              return $ map (cValueAtPosition cycList . (+ zeroPos)) groveOffsets
+          )
+
+part1 :: [Int] -> Int64
+part1 = sum . decrypt 1
+
+decryptionKey :: Int
+decryptionKey = 811589153
+
+part2 :: [Int] -> Int64
+part2 = sum . decrypt 10 . map (* decryptionKey)
+
+day :: Day
+day = parsecDay parser (definitive . part1, definitive . part2)

src/Lib.hs

@@ -31,6 +31,7 @@ import Days.D16 qualified as D16
 import Days.D17 qualified as D17
 import Days.D18 qualified as D18
 import Days.D19 qualified as D19
+import Days.D20 qualified as D20
 
 import Data.ByteString.Char8 qualified as BS
 import Data.Text.IO qualified as T
@@ -62,4 +63,5 @@ days =
     , [D17.day]
     , [D18.day]
     , [D19.day]
+    , [D20.day]
     ]