hee

1 files changed, 99 insertions, 0 deletions

diff --git a/2021/14/solve.c b/2021/14/solve.c
new file mode 100644
index 0000000..b8c49f0
--- /dev/null
+++ b/2021/14/solve.c
@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.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 IDX(a, b) (((a) - 'A') * 26 + ((b) - 'A'))
+#define LEFT(i) (((i) / 26) + 'A')
+#define RIGHT(i) (((i) % 26) + 'A')
+static void solve(FILE *fp)
+{
+	char input[32] = { 0 };
+	char rules[26 * 26] = { 0 };
+
+	int klaus = 0;
+	FORLINE
+	{
+		if (!klaus)
+			strcpy(input, line);
+		else if (klaus >= 2)
+			rules[IDX(line[0], line[1])] = line[6];
+		klaus++;
+	}
+	FREELINE;
+
+	long pairs[26 * 26] = { 0 };
+	long counts[26] = { 0 };
+
+	for (char *p = input; *p && *p != '\n'; p++) {
+		if (*(p + 1))
+			pairs[IDX(*p, *(p + 1))] += 1;
+		counts[*p - 'A'] += 1;
+	}
+
+	int start = 0, end = 10;
+aah:
+	for (int i = start; i < end; i++) {
+		long new[26 * 26] = { 0 };
+		for (int j = 0; j < COUNT(pairs); j++) {
+			char a = LEFT(j), b = RIGHT(j);
+			char insert = rules[IDX(a, b)];
+			if (insert) {
+				new[IDX(a, insert)] += pairs[j];
+				new[IDX(insert, b)] += pairs[j];
+				counts[insert - 'A'] += pairs[j];
+			} else {
+				new[j] = pairs[j];
+			}
+		};
+
+		memcpy(pairs, new, sizeof(pairs));
+	}
+
+	long max = 0, min = 0x4242424242424242;
+	for (int i = 0; i < COUNT(counts); i++) {
+		if (!counts[i])
+			continue;
+
+		if (counts[i] > max)
+			max = counts[i];
+		else if (counts[i] < min)
+			min = counts[i];
+	}
+
+	printf("%lu\n", max - min);
+
+	if (start == 0) {
+		start = end;
+		end = 40;
+		goto aah;
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	(void)argc;
+	(void)argv;
+
+	FILE *fp = fopen("input", "r");
+	if (!fp)
+		exit(EXIT_FAILURE);
+
+	clock_t tic = clock();
+	solve(fp);
+	clock_t toc = clock();
+	printf("TIME: %f seconds\n", (double)(toc - tic) / CLOCKS_PER_SEC);
+
+	fclose(fp);
+	return 0;
+}