From 300454fd7c51de7383f7cf816938204fa20d79fe Mon Sep 17 00:00:00 2001
From: Adam Spragg <adam@spra.gg>
Date: Wed, 14 Dec 2022 18:39:00 +0000
Subject: Solve puzzle 14 part 1
---
14.c | 228 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
makefile | 1 +
2 files changed, 229 insertions(+)
create mode 100644 14.c
diff --git a/14.c b/14.c
new file mode 100644
index 0000000..4a51c76
--- /dev/null
+++ b/14.c
@@ -0,0 +1,228 @@
+
+#include <regex.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+
+#define arrlen(x) (sizeof(x)/sizeof((x)[0]))
+
+
+int
+cavepos(int xmin, int xmax, int ymax, int x, int y)
+{
+ if (x < xmin || x > xmax || y < 0 || y > ymax) {
+ fprintf(stderr, "%s: %d/%d/%d/%d/%d\n", __FUNCTION__, xmin, xmax, ymax, x, y);
+ return 0;
+ }
+ return x - xmin + y * (1 + xmax - xmin);
+}
+
+
+int
+cave_resize(char ** cave, int * xmin, int * xmax, int * ymax,
+ int x, int y)
+{
+ int newxmin, newxmax, newymax;
+ void * p;
+
+ if (y < 0)
+ // Oops
+ return -1;
+
+ if (y <= *ymax && x >= *xmin && x <= *xmax)
+ // Nothing to do.
+ return 0;
+
+ newxmin = x < *xmin ? x : *xmin;
+ newxmax = x > *xmax ? x : *xmax;
+ newymax = y > *ymax ? y : *ymax;
+
+ p = calloc(newymax + 1, 1 + newxmax - newxmin);
+ if (!p)
+ return -1;
+
+ if (*cave) {
+ int i;
+ for (i = 0; i <= *ymax; ++i) {
+ memcpy(p + i * (1 + newxmax - newxmin) + *xmin - newxmin,
+ *cave + i * (1 + *xmax - *xmin),
+ 1 + *xmax - *xmin);
+ }
+ free(*cave);
+ }
+
+ *cave = p;
+ *xmin = newxmin;
+ *xmax = newxmax;
+ *ymax = newymax;
+
+ return 0;
+}
+
+
+#if 0
+void
+cave_dump(char * cave, int xmin, int xmax, int ymax)
+{
+ int x, y;
+
+ for (y = 0; y <= ymax; ++y) {
+ for (x = xmin; x <= xmax; ++x) {
+ char c = cave[cavepos(xmin, xmax, ymax, x, y)];
+ fputc(c ? c : '.', stderr);
+ }
+ fputc('\n', stderr);
+ }
+ fputc('\n', stderr);
+}
+#endif
+
+
+int
+main()
+{
+ regex_t coords;
+ char buf[BUFSIZ];
+ char * cave = NULL;
+ int xmin = 500, xmax = 500, ymax = 0;
+ int grain;
+
+ if (regcomp(&coords, "( -> )?([[:digit:]]+),([[:digit:]]+)", REG_EXTENDED) != 0) {
+ fprintf(stderr, "Bad regex\n");
+ return -1;
+ }
+
+ // Read the cave
+ while (fgets(buf, sizeof(buf), stdin)) {
+ char * pos;
+ int x, y;
+ regmatch_t xy[4];
+
+ pos = buf;
+ if (regexec(&coords, pos, arrlen(xy), xy, 0) != 0) {
+ fprintf(stderr, "No coords found in %s\n", pos);
+ free(cave);
+ regfree(&coords);
+ return -1;
+ }
+ x = atoi(buf + xy[2].rm_so);
+ y = atoi(buf + xy[3].rm_so);
+ if (cave_resize(&cave, &xmin, &xmax, &ymax, x, y) != 0) {
+ fprintf(stderr, "Unable to resize cave for %d,%d\n", x, y);
+ free(cave);
+ regfree(&coords);
+ return -1;
+ }
+ pos += xy[0].rm_eo;
+
+ while (regexec(&coords, pos, arrlen(xy), xy, 0) == 0) {
+ int newx, newy, i;
+
+ newx = atoi(pos + xy[2].rm_so);
+ newy = atoi(pos + xy[3].rm_so);
+ if (cave_resize(&cave, &xmin, &xmax, &ymax, newx, newy) != 0) {
+ fprintf(stderr, "Unable to resize cave for %d,%d\n", newx, newy);
+ free(cave);
+ regfree(&coords);
+ return -1;
+ }
+
+ if ((newx != x && newy != y)
+ || (newx == x && newy == y))
+ {
+ fprintf(stderr, "Unexpected %d,%d -> %d,%d\n", x, y, newx, newy);
+ }
+ else if (newx != x) {
+ for (i = x; i < newx; ++i) {
+ cave[cavepos(xmin, xmax, ymax, i, y)] = '#';
+ }
+ for (i = x; i > newx; --i) {
+ cave[cavepos(xmin, xmax, ymax, i, y)] = '#';
+ }
+ }
+ else if (newy != y) {
+ for (i = y; i < newy; ++i) {
+ cave[cavepos(xmin, xmax, ymax, x, i)] = '#';
+ }
+ for (i = y; i > newy; --i) {
+ cave[cavepos(xmin, xmax, ymax, x, i)] = '#';
+ }
+ }
+
+ x = newx;
+ y = newy;
+ pos += xy[0].rm_eo;
+ }
+
+ cave[cavepos(xmin, xmax, ymax, x, y)] = '#';
+
+ if (*pos != '\n') {
+ fprintf(stderr, "Unexpected remaining line: %s\n", pos);
+ }
+ }
+
+#if 0
+ cave_dump(cave, xmin, xmax, ymax);
+#endif
+
+ // Simulate sand
+ for (grain = 0; 1; ++grain) {
+ int x, y;
+
+ x = 500;
+
+ if (cave[cavepos(xmin, xmax, ymax, x, 0)] != '\0')
+ // Grain can't enter the cave!
+ 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.
+ for (y = 0; y < ymax; ++y) {
+ if (cave[cavepos(xmin, xmax, ymax, x, y + 1)] == '\0') {
+ // Do nothing, drop down one
+ (void) 0;
+ }
+ 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
+ --x;
+ }
+ 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
+ ++x;
+ }
+ else {
+ // Settle
+ cave[cavepos(xmin, xmax, ymax, x, y)] = 'o';
+ break;
+ }
+ }
+
+#if 0
+ cave_dump(cave, xmin, xmax, ymax);
+#endif
+
+ if (x < xmin || x > xmax || y >= ymax)
+ // Grain fell out of cave
+ break;
+ }
+
+ printf("Grains: %d\n", grain);
+
+ free(cave);
+ regfree(&coords);
+
+ return 0;
+}
+
diff --git a/makefile b/makefile
index 05247f8..9c956b4 100644
--- a/makefile
+++ b/makefile
@@ -15,6 +15,7 @@ all: bin \
bin/11 \
bin/12 \
bin/13 \
+ bin/14 \
bin:
mkdir -p $@
--
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