solve day 20

day20.c

@@ -0,0 +1,190 @@
+#include <stdio.h>
+#include <assert.h>
+
+#include "types.h"
+#include "aoc.h"
+
+typedef struct {
+	i64 *numbers;
+	u32 count;
+} day20_data;
+
+typedef struct day20_node *day20_node_ptr;
+struct day20_node {
+	i64 value;
+	day20_node_ptr next;
+	day20_node_ptr prev;
+};
+
+static void* day20_parse(char** lines, int line_count)
+{
+	day20_data *data = malloc(sizeof(day20_data));
+	data->numbers = malloc(sizeof(i64) * line_count);
+	data->count = line_count;
+
+	for (int i = 0; i < line_count; i++) {
+		data->numbers[i] = strtol(lines[i], NULL, 10);
+	}
+
+	return data;
+}
+
+static struct day20_node *day20_list_alloc(i64 *values, u32 count)
+{
+	struct day20_node *start = calloc(1, sizeof(struct day20_node));
+	start->value = values[0];
+	start->next = NULL;
+
+	struct day20_node *prev = start;
+	for (int i = 1; i < count; i++) {
+		struct day20_node *curr = calloc(1, sizeof(struct day20_node));
+		curr->value = values[i];
+		curr->prev = prev;
+		prev->next = curr;
+		prev = curr;
+	}
+
+	prev->next = start;
+	start->prev = prev;
+
+	return start;
+}
+
+static void day20_list_free(struct day20_node *list)
+{
+	struct day20_node *curr = list;
+	curr->prev->next = NULL;
+	while (curr) {
+		struct day20_node *next = curr->next;
+		curr->next = NULL;
+		free(curr);
+		curr = next;
+	}
+}
+
+static struct day20_node *day20_list_get(struct day20_node *list, i64 nth, u32 list_size)
+{
+	struct day20_node *curr = list;
+	if (nth > 0) {
+		for (int i = 0; i < nth % list_size; i++) {
+			curr = curr->next;
+		}
+	} else if (nth < 0) {
+		for (int i = 0; i < (-nth+1) % list_size; i++) {
+			curr = curr->prev;
+		}
+	}
+	return curr;
+}
+
+static struct day20_node *day20_list_find(struct day20_node *list, i64 value)
+{
+	struct day20_node *curr = list;
+	do {
+		if (curr->value == value) {
+			return curr;
+		}
+		curr = curr->next;
+	} while (curr != list);
+	return NULL;
+}
+
+static void day20_node_remove(struct day20_node *node)
+{
+	struct day20_node *prev = node->prev;
+	struct day20_node *next = node->next;
+
+	prev->next = next;
+	next->prev = prev;
+}
+
+static void day20_node_insert_after(struct day20_node *node, struct day20_node *new_node)
+{
+	struct day20_node *next = node->next;
+
+	new_node->prev = node;
+	new_node->next = next;
+	node->next = new_node;
+	next->prev = new_node;
+}
+
+static void day20_print_list(struct day20_node *list)
+{
+	struct day20_node *curr = list;
+	do {
+		printf("%ld ", curr->value);
+		curr = curr->next;
+	} while (curr != list);
+	printf("\n");
+}
+
+static void day20_mix_list(struct day20_node **order, u32 count)
+{
+	for (int i = 0; i < count; i++) {
+		struct day20_node *curr = order[i];
+		if (curr->value == 0) continue;
+
+		day20_node_remove(curr);
+		struct day20_node *other = day20_list_get(curr, curr->value, count-1);
+		day20_node_insert_after(other, curr);
+	}
+}
+
+static void day20_part1(void *p)
+{
+	day20_data *data = (day20_data*)p;
+
+	struct day20_node *list = day20_list_alloc(data->numbers, data->count);
+
+	struct day20_node *order[data->count];
+	order[0] = list;
+	for (int i = 1; i < data->count; i++)
+	{
+		order[i] = order[i-1]->next;
+	}
+
+	day20_mix_list(order, data->count);
+
+	i64 answer = 0;
+	struct day20_node *zero_node = day20_list_find(list, 0);
+	answer += day20_list_get(zero_node, 1000, data->count)->value;
+	answer += day20_list_get(zero_node, 2000, data->count)->value;
+	answer += day20_list_get(zero_node, 3000, data->count)->value;
+	printf("%ld\n", answer);
+
+	day20_list_free(list);
+}
+
+static void day20_part2(void *p)
+{
+	day20_data *data = (day20_data*)p;
+
+	i64 decryption_key = 811589153;
+	for (int i = 0; i < data->count; i++) {
+		data->numbers[i] *= decryption_key;
+	}
+
+	struct day20_node *list = day20_list_alloc(data->numbers, data->count);
+
+	struct day20_node *order[data->count];
+	order[0] = list;
+	for (int i = 1; i < data->count; i++)
+	{
+		order[i] = order[i-1]->next;
+	}
+
+	for (int i = 0; i < 10; i++) {
+		day20_mix_list(order, data->count);
+	}
+
+	i64 answer = 0;
+	struct day20_node *zero_node = day20_list_find(list, 0);
+	answer += day20_list_get(zero_node, 1000, data->count)->value;
+	answer += day20_list_get(zero_node, 2000, data->count)->value;
+	answer += day20_list_get(zero_node, 3000, data->count)->value;
+	printf("%ld\n", answer);
+
+	day20_list_free(list);
+}
+
+ADD_SOLUTION(20, day20_parse, day20_part1, day20_part2);

main.c

@@ -28,6 +28,7 @@
 #include "day17.c"
 #include "day18.c"
 #include "day19.c"
+#include "day20.c"
 
 Solution *find_solution(int day)
 {
@@ -184,12 +185,14 @@ int main(int argc, char** argv) {
 	printf("part1:\n");
 	start_time = get_current_time_us();
 	solution->part1(parsed);
-	printf("Part 1 took %ldus\n\n", get_current_time_us() - start_time);
+	u64 part1_duration = get_current_time_us() - start_time;
+	printf("Part 1 took %ldus (%ldms)\n\n", part1_duration, part1_duration/1000);
 
 	printf("part2:\n");
 	start_time = get_current_time_us();
 	solution->part2(parsed);
-	printf("Part 2 took %ldus\n", get_current_time_us() - start_time);
+	u64 part2_duration = get_current_time_us() - start_time;
+	printf("Part 2 took %ldus (%ldms)\n", part2_duration, part2_duration/1000);
 
 	return 0;
 }