1 files changed, 37 insertions, 0 deletions
diff --git a/2020/05/seatids.c b/2020/05/seatids.c
new file mode 100644
index 0000000..9c3b797
--- /dev/null
+++ b/2020/05/seatids.c
@@ -0,0 +1,37 @@
+#include <math.h>
+#include <stdio.h>
+
+/* Parse the input file `input` and print out all of the seat IDs which can be piped into both awk
+ * scripts
+ */
+int
+main(void)
+{
+	FILE *fpt = fopen("input", "r");
+	/* +2 for \n and \0 */
+	char bpass[12];
+	while (fgets(bpass, 12, fpt) != NULL) {
+		int lower_r = 0;
+		int upper_r = 127;
+		for (int i = 0; i < 7; i++) {
+			if (bpass[i] == 'F')
+				upper_r = (upper_r + lower_r) / 2;
+			else
+				lower_r = round((upper_r + lower_r) / 2);
+		}
+
+		int lower_c = 0;
+		int upper_c = 7;
+		for (int i = 7; i < 10; i++) {
+			if (bpass[i] == 'L')
+				upper_c = (upper_c + lower_c) / 2;
+			else
+				lower_c = round((upper_c + lower_c) / 2);
+		}
+
+		int seat_id = upper_r * 8 + upper_c;
+		printf("%d\n", seat_id);
+	}
+
+	return 0;
+}