From a622aa41088ddf29d38c50e2032ca84984b0e12b Mon Sep 17 00:00:00 2001
From: Mart Lubbers <mart@martlubbers.net>
Date: Tue, 14 Dec 2021 10:52:48 +0100
Subject: [PATCH] day 14 part twoq

---
 14a.c |  2 +-
 14b.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 14b.c

diff --git a/14a.c b/14a.c
index c97d360..7b52084 100644
--- a/14a.c
+++ b/14a.c
@@ -25,7 +25,7 @@ int main()
 		HASH_ADD(hh, template, key, sizeof(struct pair), t);
 	}
 
-	for (int i = 0; i<10; i++) {
+	for (int i = 0; i<20; i++) {
 		free(oldinput);
 		oldinput = input;
 		input = malloc(inputlen *= 2);
diff --git a/14b.c b/14b.c
new file mode 100644
index 0000000..83ebab0
--- /dev/null
+++ b/14b.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <limits.h>
+#include <string.h>
+
+#define lookup(i, x1, x2) (i)[((x1)-'A')+((x2)-'A')*26]
+
+int main()
+{
+	char *buf = NULL;
+	size_t len;
+	char template[26*26] = {0};
+	unsigned long input1[26*26] = {0};
+	unsigned long input2[26*26] = {0};
+	unsigned long *input = input1;
+	unsigned long *newinput = input2;
+
+	int first = getchar();
+	int c, oldc = first;
+	unsigned long freq[26] = {0};
+	while ( (c = getchar()) != '\n') {
+		lookup(input, oldc, c) = 1;
+		oldc = c;
+	}
+
+	while (getline(&buf, &len, stdin) != -1) {
+		if (buf[0] == '\n')
+			continue;
+		lookup(template, buf[0], buf[1]) = buf[6];
+	}
+
+	for (int step = 0; step < 40; step++) {
+		for (char x = 'A'; x<='Z'; x++) {
+			for (char y = 'A'; y<='Z'; y++) {
+				char ins = lookup(template, x, y);
+				if (ins != '\0') {
+					unsigned long freq = lookup(input, x, y);
+					lookup(newinput, x, ins) += freq;
+					lookup(newinput, ins, y) += freq;
+				}
+			}
+		}
+		unsigned long *t = newinput;
+		newinput = input;
+		input = t;
+		memset(&newinput[0], 0, sizeof(input1));
+	}
+
+	for (char x = 'A'; x<='Z'; x++) {
+		for (char y = 'A'; y<='Z'; y++) {
+			freq[x-'A'] += lookup(input, x, y);
+			freq[y-'A'] += lookup(input, x, y);
+		}
+	}
+	freq[first-'A']++;
+	freq[oldc-'A']++;
+
+	unsigned long min = ULONG_MAX, max = 0;
+	for (int i = 0; i<26; i++) {
+		max = freq[i] > max ? freq[i] : max;
+		min = freq[i] > 1 && freq[i] < min ? freq[i] : min;
+	}
+
+	printf("%lu\n", max/2-min/2);
+}
-- 
2.20.1