Merry christmas!

3 files changed, 58 insertions, 0 deletions

diff --git a/2020/25/Makefile b/2020/25/Makefile
new file mode 100644
index 0000000..fc2ff1a
--- /dev/null
+++ b/2020/25/Makefile
@@ -0,0 +1,10 @@
+.PHONY: solve.c
+
+solve.o: solve.c
+	@gcc -Ofast $+ -o $@
+
+clean:
+	@rm -f *.o
+
+run: solve.o
+	@./solve.o
diff --git a/2020/25/input b/2020/25/input
new file mode 100644
index 0000000..5ef34a0
--- /dev/null
+++ b/2020/25/input
@@ -0,0 +1,2 @@
+11349501
+5107328
diff --git a/2020/25/solve.c b/2020/25/solve.c
new file mode 100644
index 0000000..fd6542e
--- /dev/null
+++ b/2020/25/solve.c
@@ -0,0 +1,46 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define MAGIC 20201227
+
+long part_one(FILE *fp)
+{
+	long res = 1;
+
+	int pub1, pub2;
+	fscanf(fp, "%d\n%d", &pub1, &pub2);
+
+	int loop1 = 1;
+	long val = 1;
+	while (val != pub1 && loop1++)
+		val = (val * 7) % MAGIC;
+
+	for (int i = 0; i < loop1 - 1; i++)
+		res = (res * pub2) % MAGIC;
+	return res;
+}
+
+long part_two(FILE *fp)
+{
+	long res = 0;
+	// Merry christmas!
+	return res;
+}
+
+int main(int argc, char *argv[])
+{
+	FILE *fp = fopen("input", "r");
+	if (!fp)
+		exit(EXIT_FAILURE);
+
+	clock_t tic = clock();
+	printf("%lu\n", part_one(fp));
+	rewind(fp);
+	printf("%lu\n", part_two(fp));
+	clock_t toc = clock();
+	printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
+
+	fclose(fp);
+	return 0;
+}