1 files changed, 92 insertions, 0 deletions
diff --git a/6/1.c b/6/1.c
new file mode 100644
index 0000000..2a8504e
--- /dev/null
+++ b/6/1.c
@@ -0,0 +1,92 @@
+#include <assert.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+enum {
+	WIDTH = 1000,
+	HEIGHT = 1000,
+};
+
+struct instr {
+	enum action {
+		A_OFF,
+		A_ON,
+		A_TOGGLE,
+	} act;
+	struct pos {
+		unsigned short x, y;
+	} start, end;
+};
+
+unsigned short read_be16(void *_buf)
+{
+	unsigned char *buf = _buf;
+	return (buf[0] << 8) | buf[1];
+}
+
+bool read_instr(struct instr *i, FILE *f)
+{
+	unsigned char buf[9];
+	unsigned short v;
+
+	assert(i != NULL);
+	assert(f != NULL);
+
+	if (fread(buf, sizeof buf, 1, f) != 1)
+		return false;
+	switch (buf[0]) {
+	case 0xff: i->act = A_OFF; break;
+	case 1: i->act = A_ON; break;
+	case 2: i->act = A_TOGGLE; break;
+	default: return false;
+	}
+
+#define SET(f, p) { \
+		v = read_be16(&buf[p]); \
+		if (v > 999) \
+			return false; \
+		i->f = v; \
+	}
+	SET(start.x, 1);
+	SET(start.y, 3);
+	SET(end.x, 5);
+	SET(end.y, 7);
+
+	return true;
+}
+
+int main(void)
+{
+	char *map[] = { "turn off", "turn on", "toggle" };
+	bool screen[WIDTH][HEIGHT] = { 0 };
+	struct instr i;
+	int count = 0;
+	FILE *f;
+
+	f = fopen("inputbin", "rb");
+	if (f == NULL)
+		exit(EXIT_FAILURE);
+
+	while (read_instr(&i, f)) {
+		for (int y = i.start.y; y <= i.end.y; y++) {
+			for (int x = i.start.x; x <= i.end.x; x++) {
+				switch (i.act) {
+				case A_OFF: screen[x][y] = false; break;
+				case A_ON: screen[x][y] = true; break;
+				case A_TOGGLE:
+					screen[x][y] = !screen[x][y];
+					break;
+				}
+			}
+		}
+	}
+
+	fclose(f);
+
+	for (int y = 0; y < HEIGHT; y++)
+		for (int x = 0; x < WIDTH; x++)
+			count += screen[x][y];
+
+	printf("%d\n", count);
+}