Add day 3 solutions

4 files changed, 95 insertions, 0 deletions

diff --git a/2017/03/Makefile b/2017/03/Makefile
new file mode 100644
index 0000000..fd82d57
--- /dev/null
+++ b/2017/03/Makefile
@@ -0,0 +1,6 @@
+all:
+	${CC} ${CFLAGS} -o puzzle-1 puzzle-1.c
+
+.PHONY: clean
+clean:
+	rm -f puzzle-1
diff --git a/2017/03/input b/2017/03/input
new file mode 100644
index 0000000..e079a50
--- /dev/null
+++ b/2017/03/input
@@ -0,0 +1 @@
+265149
diff --git a/2017/03/puzzle-1.c b/2017/03/puzzle-1.c
new file mode 100644
index 0000000..00cebd7
--- /dev/null
+++ b/2017/03/puzzle-1.c
@@ -0,0 +1,50 @@
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define ODD(x) (x & 1)
+#define MOVE(x)                                                                                    \
+	do {                                                                                       \
+		for (int k = 0; k < j; k++) {                                                      \
+			x;                                                                         \
+			if (++m == n)                                                              \
+				goto out;                                                          \
+		}                                                                                  \
+	} while (0)
+
+int
+main(void)
+{
+	int n, x, y;
+	FILE *fp;
+
+	if (!(fp = fopen("input", "r")))
+		err(EXIT_FAILURE, "fopen");
+
+	fscanf(fp, "%d", &n);
+	fclose(fp);
+
+	x = y = 0;
+	for (int i = 1, m = 1, j = 1; i < n; i++) {
+		if (ODD(i)) {
+			if (ODD(j))
+				MOVE(x++);
+			else
+				MOVE(x--);
+		} else {
+			if (ODD(j))
+				MOVE(y++);
+			else
+				MOVE(y--);
+			j++;
+		}
+	}
+out:
+	if (x < 0)
+		x = -x;
+	if (y < 0)
+		y = -y;
+
+	printf("%d\n", x + y);
+	return EXIT_SUCCESS;
+}
diff --git a/2017/03/puzzle-2.awk b/2017/03/puzzle-2.awk
new file mode 100755
index 0000000..0758658
--- /dev/null
+++ b/2017/03/puzzle-2.awk
@@ -0,0 +1,38 @@
+#!/usr/bin/env -S awk -f
+
+function move(xi, yi)
+{
+	for (k = 0; k < j; k++) {
+		if (xi)
+			x += xi
+		else
+			y += yi
+
+		spiral[y][x] = spiral[y][x - 1] + spiral[y][x + 1] + spiral[y + 1][x + 1] \
+				+ spiral[y + 1][x] + spiral[y + 1][x - 1] + spiral[y - 1][x + 1] \
+				+ spiral[y - 1][x] + spiral[y - 1][x - 1]
+		if (spiral[y][x] > n)
+			return spiral[y][x]
+	}
+	return 0
+}
+
+{ n = $1 }
+
+END {
+	spiral[0][0] = 1
+	x = y = 0
+	j = 1
+	for (i = 1; 1; i++) {
+		if (i % 2)
+			if (r = move(j % 2 ? 1 : -1, 0))
+				break
+		else {
+			if (r = move(0, j % 2 ? 1 : -1))
+				break
+			j++
+		}
+	}
+
+	print r
+}