7 files changed, 969 insertions, 0 deletions
diff --git a/2020/05/.gitignore b/2020/05/.gitignore
new file mode 100644
index 0000000..e2451f9
--- /dev/null
+++ b/2020/05/.gitignore
@@ -0,0 +1 @@
+seatids
diff --git a/2020/05/Makefile b/2020/05/Makefile
new file mode 100644
index 0000000..48f7dd4
--- /dev/null
+++ b/2020/05/Makefile
@@ -0,0 +1,6 @@
+all:
+	${CC} ${CFLAGS} -o seatids seatids.c
+
+.PHONY: clean
+clean:
+	rm -f seatids
diff --git a/2020/05/input b/2020/05/input
new file mode 100644
index 0000000..e3bc909
--- /dev/null
+++ b/2020/05/input
@@ -0,0 +1,908 @@
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+\ No newline at end of file
diff --git a/2020/05/puzzle-1.awk b/2020/05/puzzle-1.awk
new file mode 100644
index 0000000..831c127
--- /dev/null
+++ b/2020/05/puzzle-1.awk
@@ -0,0 +1,2 @@
+$0 > max { max = $0 }
+END      { print max }
diff --git a/2020/05/puzzle-2.awk b/2020/05/puzzle-2.awk
new file mode 100644
index 0000000..8b9b823
--- /dev/null
+++ b/2020/05/puzzle-2.awk
@@ -0,0 +1,11 @@
+{ ids[NR] = $0 }
+
+END {
+	n = asort(ids)
+	for (i = 1; i <= n; i++) {
+		if ((i + 35) != ids[i]) {
+			print i + 35
+			exit
+		}
+	}
+}
diff --git a/2020/05/puzzles.sh b/2020/05/puzzles.sh
new file mode 100755
index 0000000..2066d76
--- /dev/null
+++ b/2020/05/puzzles.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+
+./seatids | awk -f puzzle-1.awk
+./seatids | gawk -f puzzle-2.awk
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;
+}