From 98c12e340a2b798aecc506821d61fa219fd5d238 Mon Sep 17 00:00:00 2001
From: Adam Spragg <adam@spra.gg>
Date: Sat, 10 Dec 2022 15:04:52 +0000
Subject: Solve puzzle 10 part 2

---
 10.c | 38 ++++++++++++++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/10.c b/10.c
index a5e3d8e..033dcdd 100644
--- a/10.c
+++ b/10.c
@@ -2,18 +2,38 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 
 int
-main()
+main(int argc, char ** argv)
 {
+	int part = 1, cyclelimit = 220;
 	int cycle;
 	char buf[BUFSIZ];
 	char * op, * arg;
 	int opcycles = 0;
 	int rx = 1, nextread = 20, interval = 40, total = 0;
 
-	for (cycle = 1; cycle <= 220; ++cycle) {
+	while ((cycle = getopt(argc, argv, "p:")) != -1) {
+		switch (cycle) {
+		case 'p':
+			part = atoi(optarg);
+			switch (part) {
+			case 1: cyclelimit = 220; break;
+			case 2: cyclelimit = 1000; break;
+			default:
+				fprintf(stderr, "Unexpected part: %d\n", part);
+				return -1;
+			}
+			break;
+
+		default:
+			return -1;
+		}
+	}
+
+	for (cycle = 1; cycle <= cyclelimit; ++cycle) {
 		// Start of cycle. Do we need to read a new instruction?
 		if (opcycles == 0) {
 			char * toksave = NULL;
@@ -39,11 +59,20 @@ main()
 		}
 
 		// Mid-cycle debugger attachment.
-		if (cycle >= nextread) {
+		if (part == 1 && cycle >= nextread) {
 			total += rx * cycle;
 			nextread += interval;
 		}
 
+		// Mid-cycle CRT output.
+		if (part == 2) {
+			int pixel = (cycle - 1) % interval;
+			int insprite = pixel >= rx - 1 && pixel <= rx + 1;
+			fputc(insprite ? '#' : '.', stdout);
+			if (pixel == interval - 1)
+				fputc('\n', stdout);
+		}
+
 		// Perform cycle. Reduce opcycle count, do actions that occur on
 		// op completion and increment cycle counter.
 		--opcycles;
@@ -55,7 +84,8 @@ main()
 		}
 	}
 
-	printf("Sum of interesting signal strengths: %d\n", total);
+	if (part == 1)
+		printf("Sum of interesting signal strengths: %d\n", total);
 
 	return 0;
 }
-- 
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