Merry christmas!

1 files changed, 127 insertions, 0 deletions

diff --git a/2021/25/solve.c b/2021/25/solve.c
new file mode 100644
index 0000000..9d21299
--- /dev/null
+++ b/2021/25/solve.c
@@ -0,0 +1,127 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#define ABS(a) ((a) < 0 ? -(a) : (a))
+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#define COUNT(a) ((int)(sizeof(a) / sizeof 0 [a]))
+
+#define FORLINE                                                                                    \
+	char *line = NULL;                                                                         \
+	size_t len = 0;                                                                            \
+	while (getline(&line, &len, fp) != EOF)
+#define FREELINE                                                                                   \
+	if (line)                                                                                  \
+	free(line)
+
+#define FORCH                                                                                      \
+	char ch = 0;                                                                               \
+	while ((ch = fgetc(fp)) != EOF)
+
+#define WHOLE                                                                                      \
+	fseek(fp, 0, SEEK_END);                                                                    \
+	long fsize = ftell(fp);                                                                    \
+	fseek(fp, 0, SEEK_SET);                                                                    \
+	char *data = malloc(fsize + 1);                                                            \
+	fread(data, 1, fsize, fp);                                                                 \
+	data[fsize] = 0;
+/* data[fsize--] = 0 */
+
+static int part_one(FILE *fp)
+{
+	int res = 0;
+
+	char grid[200][200] = { 0 };
+	char buf[200][200] = { 0 };
+
+	int line_cnt = 0;
+	FORLINE
+	strcpy(grid[line_cnt++], line);
+	FREELINE;
+
+	memcpy(buf, grid, sizeof(buf));
+	while (1) {
+		res++;
+
+		int moves = 0;
+
+		// East
+		for (int y = 0; y < line_cnt; y++) {
+			for (int x = 0; x < COUNT(grid[y]); x++) {
+				if (grid[y][x] != '>')
+					continue;
+
+				if (grid[y][x + 1] == '\n') { // End
+					if (grid[y][0] == '.') {
+						buf[y][x] = '.';
+						buf[y][0] = '>';
+						moves++;
+					}
+				} else if (grid[y][x + 1] == '.') {
+					buf[y][x] = '.';
+					buf[y][x + 1] = '>';
+					moves++;
+				}
+			}
+		}
+
+		// South
+		memcpy(grid, buf, sizeof(grid));
+		for (int y = 0; y < line_cnt; y++) {
+			for (int x = 0; x < COUNT(grid[y]); x++) {
+				if (grid[y][x] != 'v')
+					continue;
+
+				if (grid[y + 1][x] == 0) { // End
+					if (grid[0][x] == '.') {
+						buf[y][x] = '.';
+						buf[0][x] = 'v';
+						moves++;
+					}
+				} else if (grid[y + 1][x] == '.') {
+					buf[y][x] = '.';
+					buf[y + 1][x] = 'v';
+					moves++;
+				}
+			}
+		}
+
+		if (!moves)
+			break;
+
+		memcpy(grid, buf, sizeof(grid));
+	}
+
+	return res;
+}
+
+static int part_two(FILE *fp)
+{
+	int res = 42;
+
+	(void)fp;
+
+	return res;
+}
+
+int main(int argc, char *argv[])
+{
+	(void)argc;
+	(void)argv;
+
+	FILE *fp = fopen("input", "r");
+	if (!fp)
+		exit(EXIT_FAILURE);
+
+	clock_t tic = clock();
+	printf("%d\n", part_one(fp));
+	rewind(fp);
+	printf("%d\n", part_two(fp));
+	clock_t toc = clock();
+	printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
+
+	fclose(fp);
+	return 0;
+}