From 3a85d17f873259788fd17fd00ff4916df244e43b Mon Sep 17 00:00:00 2001
From: Michael Adler <therisen06@gmail.com>
Date: Fri, 15 Dec 2023 21:51:54 +0100
Subject: [PATCH] wip

---
 src/day14/solve.c | 42 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/src/day14/solve.c b/src/day14/solve.c
index 33b7b9a..47119cf 100644
--- a/src/day14/solve.c
+++ b/src/day14/solve.c
@@ -17,6 +17,12 @@
 #define FIXED_POINT '#'
 #define EMPTY '.'
 
+#define MAX_CYCLE_LEN 512
+
+#define P
+#define T XXH128_hash_t
+#include <ust.h>
+
 static char platform[MAX_DIM][MAX_DIM];
 
 static void tilt_north(int rows, int cols) {
@@ -101,6 +107,16 @@ static void print_platform(int rows, int cols) {
     }
 }
 
+static size_t hash(XXH128_hash_t *x) {
+    const size_t prime = 31;
+    size_t hash = 17;
+    hash = hash * prime + (size_t)x->low64;
+    hash = hash * prime + (size_t)x->high64;
+    return hash;
+}
+
+static int equal(XXH128_hash_t *a, XXH128_hash_t *b) { return a->low64 == b->low64 && a->high64 == b->high64; }
+
 void solve(const char *buf, size_t buf_size, Solution *result) {
     size_t pos = 0;
     int rows, cols;
@@ -123,8 +139,16 @@ void solve(const char *buf, size_t buf_size, Solution *result) {
 
     int total_cycles = 1000000000;
 
+    XXH128_hash_t hashes[MAX_CYCLE_LEN];
+    int hashes_count = 0;
+    _cleanup_(ust_XXH128_hash_t_free) ust_XXH128_hash_t seen = ust_XXH128_hash_t_init(hash, equal);
+    ust_XXH128_hash_t_reserve(&seen, MAX_CYCLE_LEN);
+
+    XXH128_hash_t duplicates[MAX_CYCLE_LEN];
+    int duplicates_count = 0;
+
     // find cycle
-    for (int cycle = 1; cycle <= 200; cycle++) {
+    for (int cycle = 1; cycle <= MAX_CYCLE_LEN; cycle++) {
         tilt_north(rows, cols);
         if (cycle == 1) { part1 = compute_total_load(rows, cols); }
 
@@ -132,8 +156,20 @@ void solve(const char *buf, size_t buf_size, Solution *result) {
         tilt_south(rows, cols);
         tilt_east(rows, cols);
 
-        XXH128_hash_t hash = XXH3_128bits(&platform[0][0], rows * cols);
-        printf("%d: %lu%lu\n", cycle, hash.low64, hash.high64);
+        XXH128_hash_t value = XXH3_128bits(&platform[0][0], rows * cols);
+        hashes[hashes_count++] = value;
+
+        ust_XXH128_hash_t_node *node = ust_XXH128_hash_t_find(&seen, value);
+        if (node != NULL) {
+            log_debug("cycle %d seen before", cycle);
+            duplicates[duplicates_count++] = value;
+        } else {
+            ust_XXH128_hash_t_insert(&seen, value);
+        }
+    }
+
+    for (int i = 0; i < duplicates_count; i++) {
+        // printf("duplicate %d: %lu%lu\n", i, duplicates[i].low64, duplicates[i].high64);
     }
 
     // print_platform(rows, cols);