day 22

CMakeLists.txt

@@ -4,6 +4,8 @@ project(AdventOfCode-2024)
 add_library(aoc aoc/aoc.c aoc/arena.c)
 target_include_directories(aoc PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/aoc)
 
+add_compile_options(-march=native -mavx2 -ftree-vectorize)
+
 file(GLOB DAY_DIRS day*)
 message("DAY_DIRS: ${DAY_DIRS}")
 foreach(DAY_DIR ${DAY_DIRS})

day-22/main.c

@@ -0,0 +1,109 @@
+#include "aoc.h"
+
+typedef union {
+    i8 values[4];
+    u32 value;
+} Sequence;
+
+typedef struct SeqEntry {
+    i16 bananas;
+} SeqEntry;
+
+#define SEQ_MAP_SIZE (19 * 19 * 19 * 19)
+typedef struct SeqMap {
+    union {
+        SeqEntry entries[19][19][19][19];
+        SeqEntry flat[SEQ_MAP_SIZE];
+    };
+    u64 present[(SEQ_MAP_SIZE + 63) / 64];
+} SeqMap;
+
+static inline u64
+prune(u64 secret) {
+    secret %= 16777216;
+    return secret;
+}
+
+static inline u64
+derive(u64 secret) {
+    secret ^= (secret * 64);
+    secret = prune(secret);
+
+    secret ^= (secret / 32);
+    secret = prune(secret);
+
+    secret ^= (secret * 2048);
+    secret = prune(secret);
+    return secret;
+}
+
+static inline u64
+seq_map_index(Sequence seq) {
+    return (seq.values[0] + 9) * 19 * 19 * 19 +
+           (seq.values[1] + 9) * 19 * 19 +
+           (seq.values[2] + 9) * 19 +
+           (seq.values[3] + 9);
+}
+
+static inline void
+seq_map_insert_if_not_present(SeqMap *map, Sequence seq, i32 bananas) {
+    u64 index = seq_map_index(seq);
+    SeqEntry *entry = map->flat + index;
+    u64 bit = 1ULL << (index % 64);
+    u8 present_index = index / 64;
+    bool present = (map->present[present_index] & bit) != 0;
+    if (!present) {
+        map->present[present_index] |= bit;
+        entry->bananas = bananas;
+    }
+}
+
+int main(int argc, char **argv) {
+    Arena *arena = make_arena(Megabytes(128));
+    Tokens input = read_lines(arena, argv[1]);
+
+    i8 *differences = ARENA_ALLOC_ARRAY(arena, i8, 2000);
+
+    u64 part_1 = 0;
+    SeqMap *buyer_map = ARENA_ALLOC(arena, SeqMap);
+    SeqMap *map = ARENA_ALLOC(arena, SeqMap);
+    for (isize i = 0; i < input.len; i++) {
+        u64 secret = (u64) parse_i64(str_trim(input.tokens[i]), *arena);
+
+        /* SeqMap buyer_map = {0}; */
+        memset(buyer_map, 0, sizeof(SeqMap));
+        i32 current_price = secret % 10;
+
+        Sequence diff = {0};
+        for (i32 j = 0; j < 2000; j++) {
+            secret = derive(secret);
+            i32 new_price = secret % 10;
+            i32 diff = new_price - current_price;
+            differences[j] = diff;
+
+            if (j >= 3) {
+                Sequence seq = { .values = { differences[j - 3], differences[j - 2], differences[j - 1], differences[j] } };
+                i32 bananas = new_price;
+                seq_map_insert_if_not_present(buyer_map, seq, bananas);
+            }
+            current_price = new_price;
+        }
+        part_1 += secret;
+
+        // Update global map with bananas from this buyer
+        SeqEntry *restrict from = buyer_map->flat;
+        SeqEntry *restrict to = map->flat;
+        for (isize i = 0; i < SEQ_MAP_SIZE; i++) {
+            to[i].bananas += from[i].bananas;
+        }
+    }
+    printf("%lu\n", part_1);
+
+    // Part 2: Find the maximum number of bananas
+    i32 part_2 = 0;
+    SeqEntry *restrict flat = map->flat;
+    for (isize i = 0; i < SEQ_MAP_SIZE; i++) {
+        part_2 = MAX(flat[i].bananas, part_2);
+    }
+    printf("%d\n", part_2);
+}

day-22/test.txt

@@ -0,0 +1,4 @@
+1
+10
+100
+2024

day-22/test2.txt

@@ -0,0 +1,4 @@
+1
+2
+3
+2024