Initial commit

5 files changed, 938 insertions, 0 deletions

diff --git a/2020/12/.gitignore b/2020/12/.gitignore
new file mode 100644
index 0000000..60d075d
--- /dev/null
+++ b/2020/12/.gitignore
@@ -0,0 +1 @@
+puzzle-[12]
diff --git a/2020/12/Makefile b/2020/12/Makefile
new file mode 100644
index 0000000..cf466dc
--- /dev/null
+++ b/2020/12/Makefile
@@ -0,0 +1,7 @@
+all:
+	${CC} ${CFLAGS} -o puzzle-1 puzzle-1.c
+	${CC} ${CFLAGS} -o puzzle-2 puzzle-2.c
+
+.PHONY: clean
+clean:
+	rm -f puzzle-[12]
diff --git a/2020/12/input b/2020/12/input
new file mode 100644
index 0000000..5e5e7be
--- /dev/null
+++ b/2020/12/input
@@ -0,0 +1,778 @@
+R90
+N2
+N2
+F94
+R90
+E3
+F2
+L90
+L90
+F66
+S5
+L90
+W3
+R90
+N3
+W2
+N2
+W1
+R90
+E3
+F100
+S4
+F66
+R180
+F96
+R90
+N2
+R90
+E2
+S3
+E1
+F65
+W4
+F6
+L180
+W2
+L90
+F95
+L90
+F97
+E2
+F36
+E2
+R90
+E4
+F98
+N4
+F70
+S1
+R270
+E1
+F13
+R90
+W1
+L90
+F82
+S2
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+F80
+N1
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+W4
+F23
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+N5
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+F91
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+N2
+F60
+E5
+S3
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+R180
+S3
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+W4
+F80
+S2
+L90
+F31
+W1
+L90
+F45
+S3
+F64
+N1
+W4
+N2
+R180
+W3
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+S1
+F7
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+W1
+S4
+E4
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+F87
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+F35
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+F68
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+F32
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+E4
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+F80
+R90
+S5
+E3
+F49
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+F27
+E1
+N2
+W4
+S3
+L90
+F100
+N1
+F28
+E2
+F88
+S1
+R90
+F14
+S4
+L180
+F93
+E1
+L90
+F64
+L90
+L90
+F84
+E4
+F69
+W1
+R90
+E5
+N2
+W1
+N3
+F10
+S2
+F64
+F10
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+N1
+F82
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+L180
+F14
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+F70
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+N3
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+L180
+F90
+L180
+S3
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+S5
+F40
+N4
+F95
\ No newline at end of file
diff --git a/2020/12/puzzle-1.c b/2020/12/puzzle-1.c
new file mode 100644
index 0000000..1a4c7ab
--- /dev/null
+++ b/2020/12/puzzle-1.c
@@ -0,0 +1,73 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int
+main(void)
+{
+	FILE *fp;
+	char cl[5];
+	int north, east;
+	int direction = 0;
+
+	if (!(fp = fopen("input", "r")))
+		err(EXIT_FAILURE, "fopen");
+
+	north = east = 0;
+	while (fgets(cl, sizeof(cl), fp) != NULL) {
+		switch (cl[0]) {
+		case 'N':
+			north += atoi(&cl[1]);
+			break;
+		case 'E':
+			east += atoi(&cl[1]);
+			break;
+		case 'S':
+			north -= atoi(&cl[1]);
+			break;
+		case 'W':
+			east -= atoi(&cl[1]);
+			break;
+		case 'L':
+			direction -= atoi(&cl[1]);
+			goto wrap;
+		case 'R':
+			direction += atoi(&cl[1]);
+
+wrap:
+			/* 0 <= direction < 360 */
+			if (direction >= 360)
+				direction -= 360;
+			else if (direction < 0)
+				direction += 360;
+			break;
+		case 'F':
+			switch (direction) {
+			case 0:
+				east += atoi(&cl[1]);
+				break;
+			case 90:
+				north -= atoi(&cl[1]);
+				break;
+			case 180:
+				east -= atoi(&cl[1]);
+				break;
+			case 270:
+				north += atoi(&cl[1]);
+				break;
+			}
+			break;
+		}
+	}
+	fclose(fp);
+
+	/* Absolute value */
+	if (north < 0)
+		north = -north;
+	if (east < 0)
+		east = -east;
+
+	printf("%d\n", north + east);
+	return EXIT_SUCCESS;
+}
diff --git a/2020/12/puzzle-2.c b/2020/12/puzzle-2.c
new file mode 100644
index 0000000..8ac34b4
--- /dev/null
+++ b/2020/12/puzzle-2.c
@@ -0,0 +1,79 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+struct coords {
+	int north;
+	int east;
+};
+
+int
+main(void)
+{
+	FILE *fp;
+	char cl[6];
+	struct coords waypoint = {1, 10};
+	struct coords ship = {0, 0};
+
+	if (!(fp = fopen("input", "r")))
+		err(EXIT_FAILURE, "fopen");
+
+	while (fgets(cl, sizeof(cl), fp) != NULL) {
+		switch (cl[0]) {
+		case 'N':
+			waypoint.north += atoi(&cl[1]);
+			break;
+		case 'E':
+			waypoint.east += atoi(&cl[1]);
+			break;
+		case 'S':
+			waypoint.north -= atoi(&cl[1]);
+			break;
+		case 'W':
+			waypoint.east -= atoi(&cl[1]);
+			break;
+		case 'F':;
+			unsigned int const val = atoi(&cl[1]);
+			ship.north += val * waypoint.north;
+			ship.east += val * waypoint.east;
+			break;
+		/* Left and right */
+		default:;
+			int direction = atoi(&cl[1]);
+
+			/* (x, y) -> (-x, -y) */
+			if (direction == 180) {
+				waypoint.north = -waypoint.north;
+				waypoint.east = -waypoint.east;
+				break;
+			}
+
+			/* 0 <= direction < 360 */
+			if (cl[0] == 'R')
+				direction = -direction + 360;
+
+			int const temp = waypoint.east;
+			if (direction == 90) {
+				/* (x, y) -> (-y, x) */
+				waypoint.east = -waypoint.north;
+				waypoint.north = temp;
+			} else {
+				/* (x, y) -> (y, -x) */
+				waypoint.east = waypoint.north;
+				waypoint.north = -temp;
+			}
+			break;
+		}
+	}
+	fclose(fp);
+
+	/* Absolute value */
+	if (ship.north < 0)
+		ship.north = -ship.north;
+	if (ship.east < 0)
+		ship.east = -ship.east;
+
+	printf("%d\n", ship.north + ship.east);
+	return EXIT_SUCCESS;
+}