13 a

3 files changed, 71 insertions, 0 deletions

diff --git a/2020/13/Makefile b/2020/13/Makefile
new file mode 100644
index 0000000..58d64e6
--- /dev/null
+++ b/2020/13/Makefile
@@ -0,0 +1,10 @@
+.PHONY: solve.c
+
+solve.o: solve.c
+	@gcc -Ofast $+ -o $@ -lm
+
+clean:
+	@rm -f *.o
+
+run: solve.o
+	@./solve.o
diff --git a/2020/13/input b/2020/13/input
new file mode 100644
index 0000000..fb48dd9
--- /dev/null
+++ b/2020/13/input
@@ -0,0 +1,2 @@
+1000495
+19,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,x,521,x,x,x,x,x,x,x,23,x,x,x,x,x,x,x,x,17,x,x,x,x,x,x,x,x,x,x,x,29,x,523,x,x,x,x,x,37,x,x,x,x,x,x,13
diff --git a/2020/13/solve.c b/2020/13/solve.c
new file mode 100644
index 0000000..b754518
--- /dev/null
+++ b/2020/13/solve.c
@@ -0,0 +1,59 @@
+#include <math.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int part_one(char *data)
+{
+	// Strange parsing
+	int note_earliest = 0, note_line = 0, note_service_index = 0;
+	int note_in_service[128] = { 0 };
+	for (char *p = data; *p; p++) {
+		if (*p == '\n') {
+			note_line++;
+			continue;
+		} else if (*p == 'x') {
+			p++;
+			continue;
+		}
+
+		if (!note_earliest && note_line == 0) {
+			sscanf(p, "%d\n", &note_earliest);
+		} else if (note_earliest && note_line == 1) {
+			sscanf(p, "%d,", &note_in_service[note_service_index]);
+			p += (int)(floor(log10(note_in_service[note_service_index])) + 1); // idk
+			note_service_index++;
+		}
+	}
+
+	// Strange loops
+	for (int time = note_earliest;; time++) {
+		for (int *bus = note_in_service; *bus != 0; bus++) {
+			if (time % *bus == 0)
+				return (time - note_earliest) * *bus;
+		}
+	}
+}
+
+int part_two(char *data)
+{
+	int res = 0;
+
+	return res;
+}
+
+#define SIZE 20000
+int main(int argc, char *argv[])
+{
+	FILE *fp = fopen("input", "r");
+	if (!fp)
+		exit(EXIT_FAILURE);
+	char buf[SIZE] = { 0 };
+	fread(buf, SIZE, 1, fp);
+
+	printf("%d\n", part_one(buf));
+	printf("%d\n", part_two(buf));
+
+	fclose(fp);
+	return 0;
+}