Solve puzzle 14 part 2

1 files changed, 51 insertions, 8 deletions

diff --git a/14.c b/14.c
index 4a51c76..d100253 100644
--- a/14.c
+++ b/14.c
@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 
 #define arrlen(x) (sizeof(x)/sizeof((x)[0]))
@@ -80,14 +81,26 @@ cave_dump(char * cave, int xmin, int xmax, int ymax)
 
 
 int
-main()
+main(int argc, char ** argv)
 {
+	int part = 1;
 	regex_t coords;
 	char buf[BUFSIZ];
 	char * cave = NULL;
 	int xmin = 500, xmax = 500, ymax = 0;
 	int grain;
 
+	while ((grain = getopt(argc, argv, "p:")) != -1) {
+		switch (grain) {
+		case 'p':
+			part = atoi(optarg);
+			break;
+
+		default:
+			return -1;
+		}
+	}
+
 	if (regcomp(&coords, "( -> )?([[:digit:]]+),([[:digit:]]+)", REG_EXTENDED) != 0) {
 		fprintf(stderr, "Bad regex\n");
 		return -1;
@@ -162,6 +175,17 @@ main()
 		}
 	}
 
+	if (part == 2) {
+		// Lowest floor is 2 below original max, of infinite width. Only
+		// need to keep track of one level of sand below
+		if (cave_resize(&cave, &xmin, &xmax, &ymax, xmin, ymax + 1) != 0) {
+			fprintf(stderr, "Unable to resize cave for %d,%d\n", xmin, xmax + 1);
+			free(cave);
+			regfree(&coords);
+			return -1;
+		}
+	}
+
 #if 0
 	cave_dump(cave, xmin, xmax, ymax);
 #endif
@@ -177,8 +201,9 @@ main()
 			break;
 
 		// Don't go to "y <= ymax" here. If the grain gets to ymax, it's
-		// falling off the bottom as there's nothing below it. And an
-		// attempt to look at the row below isn't valid.
+		// at the bottom and either falling off as there's nothing below
+		// it, or coming to rest on the infinite floor. And an attempt
+		// to look at the row below isn't valid.
 		for (y = 0; y < ymax; ++y) {
 			if (cave[cavepos(xmin, xmax, ymax, x, y + 1)] == '\0') {
 				// Do nothing, drop down one
@@ -187,7 +212,6 @@ main()
 			else if (x == xmin) {
 				// Fall off left edge
 				--x;
-				break;
 			}
 			else if (cave[cavepos(xmin, xmax, ymax, x - 1, y + 1)] == '\0') {
 				// Drop down and left
@@ -196,7 +220,6 @@ main()
 			else if (x == xmax) {
 				// Fall off right edge
 				++x;
-				break;
 			}
 			else if (cave[cavepos(xmin, xmax, ymax, x + 1, y + 1)] == '\0') {
 				// Drop down and right
@@ -207,15 +230,35 @@ main()
 				cave[cavepos(xmin, xmax, ymax, x, y)] = 'o';
 				break;
 			}
+
+			if (x < xmin || x > xmax) {
+				if (cave_resize(&cave, &xmin, &xmax, &ymax, (x < xmin ? x - 10 : x + 10), ymax) != 0) {
+					fprintf(stderr, "Unable to resize cave for %d,%d\n", x, ymax);
+					free(cave);
+					regfree(&coords);
+					return -1;
+				}
+			}
 		}
 
 #if 0
 		cave_dump(cave, xmin, xmax, ymax);
 #endif
 
-		if (x < xmin || x > xmax || y >= ymax)
-			// Grain fell out of cave
-			break;
+		if (y >= ymax) {
+			if (part == 2) {
+				// Grain at rest on infinite floor
+				cave[cavepos(xmin, xmax, ymax, x, y)] = 'o';
+			}
+			else if (part == 1) {
+				// Grain fell out of cave
+				break;
+			}
+			else {
+				fprintf(stderr, "Unexpected part %d\n", part);
+				break;
+			}
+		}
 	}
 
 	printf("Grains: %d\n", grain);