From cf4e5124cf7bd54064b9be73b95895503cda2cb7 Mon Sep 17 00:00:00 2001
From: Rokas Puzonas <rokas.puz@gmail.com>
Date: Fri, 14 Jul 2023 02:12:25 +0300
Subject: [PATCH] solve day 25

---
 day25.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 main.c  |  1 +
 2 files changed, 84 insertions(+)
 create mode 100644 day25.c

diff --git a/day25.c b/day25.c
new file mode 100644
index 0000000..e48e2a4
--- /dev/null
+++ b/day25.c
@@ -0,0 +1,83 @@
+#include <stdio.h>
+#include <string.h>
+
+#include "types.h"
+#include "aoc.h"
+
+typedef struct {
+	char **snafu_numbers;
+	u32 count;
+} day25_data;
+
+static void* day25_parse(char** lines, int line_count)
+{
+	day25_data *data = malloc(sizeof(day25_data));
+	data->snafu_numbers = lines;
+	data->count = line_count;
+	return data;
+}
+
+static u64 day25_snafu_to_decimal(char *snafu)
+{
+	u64 decimal = 0;
+	u64 power = 1;
+	for (int i = strlen(snafu)-1; i >= 0; i--) {
+		if (snafu[i] == '2') {
+			decimal += 2 * power;
+		} else if (snafu[i] == '1') {
+			decimal += 1 * power;
+		} else if (snafu[i] == '0') {
+			decimal += 0 * power;
+		} else if (snafu[i] == '-') {
+			decimal += -1 * power;
+		} else if (snafu[i] == '=') {
+			decimal += -2 * power;
+		}
+		power *= 5;
+	}
+	return decimal;
+}
+
+static void day25_print_snafu(u64 number)
+{
+	u32 length = 0;
+	char snafu[64] = { 0 };
+	while (number > 0) {
+		u32 remainder = number % 5;
+		number = number / 5;
+
+		if (0 <= remainder && remainder <= 2) {
+			snafu[length++] = '0' + remainder;
+		} else if (remainder == 3) {
+			snafu[length++] = '=';
+			number += 1;
+		} else { //if (remainder == 4) {
+			snafu[length++] = '-';
+			number += 1;
+		}
+	}
+
+	for (int i = length-1; i >= 0; i--) {
+		printf("%c", snafu[i]);
+	}
+	printf("\n");
+}
+
+static void day25_part1(void *p)
+{
+	day25_data *data = (day25_data*)p;
+
+	u64 sum = 0;
+	for (int i = 0; i < data->count; i++) {
+		sum += day25_snafu_to_decimal(data->snafu_numbers[i]);
+	}
+
+	day25_print_snafu(sum);
+}
+
+static void day25_part2(void *p)
+{
+	day25_data *data = (day25_data*)p;
+}
+
+ADD_SOLUTION(25, day25_parse, day25_part1, day25_part2);
diff --git a/main.c b/main.c
index 024632b..e381961 100644
--- a/main.c
+++ b/main.c
@@ -33,6 +33,7 @@
 #include "day22.c"
 #include "day23.c"
 #include "day24.c"
+#include "day25.c"
 
 Solution *find_solution(int day)
 {