day25p1

day25p1/Makefile

@@ -0,0 +1,12 @@
+CFLAGS := -Wall -Wextra -std=c17 -D_GNU_SOURCE
+
+LIBS := glib-2.0
+CFLAGS += $(shell pkg-config --cflags $(LIBS))
+LDLIBS := $(shell pkg-config --libs $(LIBS))
+
+.PHONY: all
+all: main
+
+.PHONY: clean
+clean:
+	rm -f main

day25p1/main.c

@@ -0,0 +1,117 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <glib.h>
+
+struct coord4d {
+    int x;
+    int y;
+    int z;
+    int t;
+};
+
+struct point {
+    struct coord4d c;
+    GPtrArray *near;
+};
+
+struct point *parse_points(const char *fname, unsigned *len)
+{
+    FILE *f = fopen(fname, "r");
+    if (!f) {
+        perror(fname);
+        return NULL;
+    }
+
+    GArray *array = g_array_new(FALSE, FALSE, sizeof(struct point));
+
+    struct point point;
+    while (fscanf(f, "%d,%d,%d,%d\n",
+                &point.c.x, &point.c.y,
+                &point.c.z, &point.c.t) == 4) {
+        point.near = g_ptr_array_new();
+        g_array_append_val(array, point);
+    }
+
+    *len = array->len;
+    return (struct point *)g_array_free(array, FALSE);
+}
+
+void free_points(struct point *points, const unsigned len)
+{
+    for (struct point *point = points;
+            point < points + len; point++) {
+        g_ptr_array_free(point->near, TRUE);
+    }
+    g_free(points);
+}
+
+GHashTable *find_const(GPtrArray *consts, struct point *point)
+{
+    for (GHashTable **p = (GHashTable **)consts->pdata;
+            p < (GHashTable **)consts->pdata + consts->len; p++) {
+        if (g_hash_table_contains(*p, point)) return *p;
+    }
+    return NULL;
+}
+
+void merge_const(GPtrArray *consts, GHashTable *a, GHashTable *b)
+{
+    if (a == b) return;
+
+    GHashTableIter iter;
+    gpointer key, value;
+    g_hash_table_iter_init(&iter, b);
+    while (g_hash_table_iter_next(&iter, &key, &value)) {
+        g_hash_table_add(a, key);
+    }
+    g_ptr_array_remove_fast(consts, b);
+}
+
+int main()
+{
+    unsigned points_len;
+    struct point *points = parse_points("input", &points_len);
+    if (!points) return 1;
+
+    for (struct point *a = points;
+            a < points + points_len; a++) {
+        for (struct point *b = points;
+                b < points + points_len; b++) {
+            unsigned x = abs(a->c.x - b->c.x);
+            unsigned y = abs(a->c.y - b->c.y);
+            unsigned z = abs(a->c.z - b->c.z);
+            unsigned t = abs(a->c.t - b->c.t);
+
+            if (x + y + z + t <= 3) {
+                g_ptr_array_add(a->near, b);
+            }
+        }
+    }
+
+    GPtrArray *consts = g_ptr_array_new();
+    g_ptr_array_set_free_func(consts, (void (*)(void *))g_hash_table_destroy);
+
+    for (struct point *p = points; p < points + points_len; p++) {
+        GHashTable *constel = find_const(consts, p);
+        if (!constel) {
+            constel = g_hash_table_new(NULL, NULL);
+            g_hash_table_add(constel, p);
+            g_ptr_array_add(consts, constel);
+        }
+
+        for (struct point **p2 = (struct point **)p->near->pdata;
+                p2 < (struct point **)p->near->pdata + p->near->len; p2++) {
+            GHashTable *constel2 = find_const(consts, *p2);
+            if (constel2) merge_const(consts, constel, constel2);
+
+            g_hash_table_add(constel, *p2);
+        }
+    }
+
+    printf("%u\n", consts->len);
+
+    g_ptr_array_free(consts, TRUE);
+    free_points(points, points_len);
+    return 0;
+}