1 files changed, 87 insertions, 0 deletions
diff --git a/2018/day17.c b/2018/day17.c
new file mode 100644
index 0000000..d2fd02c
--- /dev/null
+++ b/2018/day17.c
@@ -0,0 +1,87 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+typedef unsigned uint;
+
+static char map[2048][2048];
+
+static void draw(void) {
+	for (uint y = 0; y < 14; ++y) {
+		for (uint x = 494; x < 508; ++x) {
+			printf("%c", map[y][x]);
+		}
+		printf("\n");
+	}
+	printf("\n");
+}
+
+int main(void) {
+	memset(map, '.', sizeof(map));
+	uint minY = 2048, maxY = 0;
+	while (!feof(stdin)) {
+		char a, b;
+		uint fixed, start, end;
+		scanf("%c=%u, %c=%u..%u\n", &a, &fixed, &b, &start, &end);
+		for (uint i = start; i <= end; ++i) {
+			if (a == 'y') {
+				map[fixed][i] = '#';
+			} else {
+				map[i][fixed] = '#';
+			}
+		}
+		if (a == 'y') {
+			if (fixed < minY) minY = fixed;
+			if (fixed > maxY) maxY = fixed;
+		} else {
+			if (start < minY) minY = start;
+			if (end > maxY) maxY = end;
+		}
+	}
+	map[0][500] = '|';
+
+	bool hot;
+	do {
+		hot = false;
+		for (uint y = 0; y < 2047; ++y) {
+			for (uint x = 0; x < 2048; ++x) {
+				char *self = &map[y][x];
+				char *below = &map[y + 1][x];
+				char *left = &map[y][x - 1];
+				char *right = &map[y][x + 1];
+				if (*self != '|' && *self != '*') continue;
+				if (*below == '.') {
+					*below = '|';
+					hot = true;
+				}
+				if (*below != '#' && *below != '~') continue;
+				if (*left == '.') {
+					*left = '|';
+					hot = true;
+				}
+				if (*right == '.') {
+					*right = '|';
+					hot = true;
+				}
+				if (*self == '|' && (*left == '#' || *left == '*')) {
+					*self = '*';
+					hot = true;
+				}
+				if (*self == '*' && (*right == '#' || *right == '~')) {
+					*self = '~';
+					hot = true;
+				}
+			}
+		}
+	} while (hot);
+	draw();
+
+	uint count = 0;
+	for (uint y = minY; y <= maxY; ++y) {
+		for (uint x = 0; x < 2048; ++x) {
+			if (map[y][x] != '.' && map[y][x] != '#') count++;
+		}
+	}
+	printf("%u\n", count);
+}