Efficiency

1 files changed, 81 insertions, 0 deletions

diff --git a/2021/06/solve.c b/2021/06/solve.c
new file mode 100644
index 0000000..069cb09
--- /dev/null
+++ b/2021/06/solve.c
@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#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 long iterate(char *fish, long cnt)
+{
+	/* for (int i = 0; i < cnt; i++) */
+	/* 	printf("%d,", fish[i]); */
+	/* printf("\n"); */
+
+	long ret = cnt;
+	for (long i = 0; i < cnt; i++) {
+		if (fish[i] == 0) {
+			fish[i] = 6;
+			fish[ret++] = 8;
+		} else {
+			fish[i]--;
+		}
+	}
+
+	return ret;
+}
+
+static long solve(FILE *fp)
+{
+	char *fish = malloc(20000000000 * sizeof(char));
+
+	long cnt = 0;
+	char ch;
+	while (fscanf(fp, "%d%c", (int *)&fish[cnt++], &ch) != EOF && (ch == ',' || ch == '\n'))
+		;
+	cnt -= 1; // newline
+
+	for (int i = 0; i < 256; i++)
+		cnt = iterate(fish, cnt);
+
+	free(fish);
+
+	return cnt;
+}
+
+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("%lu\n", solve(fp));
+	clock_t toc = clock();
+	printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
+
+	fclose(fp);
+	return 0;
+}