From ef8b789d18ba128f34a00ed8e789e664395e43ad Mon Sep 17 00:00:00 2001
From: tomsmeding <tom.smeding@gmail.com>
Date: Mon, 25 Dec 2017 11:27:04 +0100
Subject: Christmas! 🎄
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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---
2017/25.c | 151 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
2017/25.in | 62 +++++++++++++++++++++++++
2 files changed, 213 insertions(+)
create mode 100644 2017/25.c
create mode 100644 2017/25.in
(limited to '2017')
diff --git a/2017/25.c b/2017/25.c
new file mode 100644
index 0000000..46680d4
--- /dev/null
+++ b/2017/25.c
@@ -0,0 +1,151 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+#include <ctype.h>
+#include <assert.h>
+
+
+const char* next_word(void){
+ static char buf[1024];
+ int len=0;
+ char c=getchar();
+ while(isspace(c))c=getchar();
+ if(feof(stdin))return NULL;
+ if(!isalnum(c)){
+ buf[0]=c;
+ buf[1]='\0';
+ return buf;
+ }
+ while(isalnum(c)&&!feof(stdin)){
+ buf[len++]=c;
+ c=getchar();
+ }
+ if(!feof(stdin))ungetc(c,stdin);
+ buf[len]='\0';
+ return buf;
+}
+
+struct rule {
+ int state;
+ int direction; // right = 1, left = -1
+ bool value;
+};
+
+struct rules {
+ struct rule table[8][2];
+ int start;
+ int stopcount;
+};
+
+
+#define EQ(s1_,s2_) (strcmp((s1_),(s2_))==0)
+#define READ(dest_) assert((dest_)=next_word())
+#define READ_EOF(dest_) ((dest_)=next_word())
+#define READSTATE(dest_) ((dest_)=next_word()[0]-'A')
+#define READINT(dest_) ((dest_)=strtol(next_word(),NULL,10))
+#define EXPECT(s_) assert(EQ(next_word(),(s_)))
+
+static struct rules parse(void){
+ struct rules R;
+ int curstate=0,curval=0;
+ const char *word;
+ while(true){
+ READ_EOF(word);
+ if(!word)break;
+ if(EQ(word,"Begin")){
+ EXPECT("in"); EXPECT("state");
+ READSTATE(R.start);
+ EXPECT(".");
+ } else if(EQ(word,"Perform")){
+ EXPECT("a"); EXPECT("diagnostic"); EXPECT("checksum"); EXPECT("after");
+ READINT(R.stopcount);
+ EXPECT("steps"); EXPECT(".");
+ } else if(EQ(word,"In")){
+ EXPECT("state");
+ READSTATE(curstate);
+ EXPECT(":");
+ } else if(EQ(word,"If")){
+ EXPECT("the"); EXPECT("current"); EXPECT("value"); EXPECT("is");
+ READINT(curval);
+ EXPECT(":");
+ } else if(EQ(word,"-")){
+ READ(word);
+ if(EQ(word,"Write")){
+ EXPECT("the"); EXPECT("value");
+ READINT(R.table[curstate][curval].value);
+ EXPECT(".");
+ } else if(EQ(word,"Move")){
+ EXPECT("one"); EXPECT("slot"); EXPECT("to"); EXPECT("the");
+ READ(word);
+ if(EQ(word,"right"))R.table[curstate][curval].direction=1;
+ else if(EQ(word,"left"))R.table[curstate][curval].direction=-1;
+ else assert(false);
+ EXPECT(".");
+ } else if(EQ(word,"Continue")){
+ EXPECT("with"); EXPECT("state");
+ READSTATE(R.table[curstate][curval].state);
+ EXPECT(".");
+ } else {
+ assert(false);
+ }
+ } else {
+ assert(false);
+ }
+ }
+ return R;
+}
+
+#undef EQ
+#undef EXPECT
+
+static void printrules(const struct rules R){
+ printf("start=%c\nstopcount=%d\n",R.start+'A',R.stopcount);
+ for(int i=0;i<8;i++){
+ printf("%c: %d,%c,%c %d,%c,%c\n",
+ 'A'+i,
+ R.table[i][0].value,"<>"[R.table[i][0].direction],R.table[i][0].state+'A',
+ R.table[i][1].value,"<>"[R.table[i][1].direction],R.table[i][1].state+'A');
+ }
+}
+
+int main(void){
+ freopen("25.in","r",stdin);
+ struct rules R=parse();
+ // printrules(R);
+
+ assert(sizeof(bool)==1);
+
+ int tapesize=4096;
+ bool *tape=calloc(tapesize,1);
+
+ int state=R.start,ptr=tapesize/2;
+
+ for(int iter=0;iter<R.stopcount;iter++){
+ if(ptr==-1){
+ bool *newtape=calloc(2*tapesize,1);
+ memcpy(newtape+tapesize,tape,tapesize);
+ ptr+=tapesize;
+ free(tape);
+ tape=newtape;
+ tapesize*=2;
+ } else if(ptr==tapesize){
+ bool *newtape=calloc(2*tapesize,1);
+ memcpy(newtape,tape,tapesize);
+ free(tape);
+ tape=newtape;
+ tapesize*=2;
+ }
+ struct rule *rule=&R.table[state][tape[ptr]];
+ tape[ptr]=rule->value;
+ ptr+=rule->direction;
+ state=rule->state;
+ }
+
+ int total=0;
+ for(int i=0;i<tapesize;i++)total+=tape[i];
+ printf("%d\n",total);
+
+ free(tape);
+}
diff --git a/2017/25.in b/2017/25.in
new file mode 100644
index 0000000..e2e4d56
--- /dev/null
+++ b/2017/25.in
@@ -0,0 +1,62 @@
+Begin in state A.
+Perform a diagnostic checksum after 12399302 steps.
+
+In state A:
+ If the current value is 0:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state B.
+ If the current value is 1:
+ - Write the value 0.
+ - Move one slot to the right.
+ - Continue with state C.
+
+In state B:
+ If the current value is 0:
+ - Write the value 0.
+ - Move one slot to the left.
+ - Continue with state A.
+ If the current value is 1:
+ - Write the value 0.
+ - Move one slot to the right.
+ - Continue with state D.
+
+In state C:
+ If the current value is 0:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state D.
+ If the current value is 1:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state A.
+
+In state D:
+ If the current value is 0:
+ - Write the value 1.
+ - Move one slot to the left.
+ - Continue with state E.
+ If the current value is 1:
+ - Write the value 0.
+ - Move one slot to the left.
+ - Continue with state D.
+
+In state E:
+ If the current value is 0:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state F.
+ If the current value is 1:
+ - Write the value 1.
+ - Move one slot to the left.
+ - Continue with state B.
+
+In state F:
+ If the current value is 0:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state A.
+ If the current value is 1:
+ - Write the value 1.
+ - Move one slot to the right.
+ - Continue with state E.
--
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