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%{
#include <err.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
/* Shut up the compiler */
int fileno(FILE *);
struct Instr {
enum {
HLF,
INC,
JIE,
JIO,
JMP,
TPL
} type;
enum {
A,
B
} reg;
int imm;
};
int i = 0;
struct Instr *program;
#ifdef PART2
unsigned long long registers[2] = {1, 0};
#else
unsigned long long registers[2];
#endif
%}
%x ARGS
%%
hlf { program[i].type = HLF; BEGIN(ARGS); }
inc { program[i].type = INC; BEGIN(ARGS); }
jie { program[i].type = JIE; BEGIN(ARGS); }
jio { program[i].type = JIO; BEGIN(ARGS); }
jmp { program[i].type = JMP; BEGIN(ARGS); }
tpl { program[i].type = TPL; BEGIN(ARGS); }
<ARGS>[ab] { program[i].reg = *yytext - 'a'; }
<ARGS>[+\-][0-9]+ { program[i].imm = atoi(yytext); }
<ARGS>[ ,]+ { ; }
<ARGS>\n { i++; BEGIN(INITIAL); }
%%
static unsigned long long
execute(void)
{
for (i = 0; i < PROGLEN; i++) {
switch (program[i].type) {
case HLF:
registers[program[i].reg] /= 2;
break;
case INC:
registers[program[i].reg]++;
break;
case JIE:
if (!(registers[program[i].reg] & 1))
i += program[i].imm - 1;
break;
case JIO:
if (registers[program[i].reg] == 1)
i += program[i].imm - 1;
break;
case JMP:
i += program[i].imm - 1;
break;
case TPL:
registers[program[i].reg] *= 3;
break;
}
}
return registers[B];
}
int
main(void)
{
FILE *fp;
if (!(program = calloc(PROGLEN, sizeof(struct Instr))))
err(EXIT_FAILURE, "calloc");
if (!(fp = fopen("input", "r")))
err(EXIT_FAILURE, "fopen");
yyrestart(fp);
yylex();
fclose(fp);
printf("%llu\n", execute());
return EXIT_SUCCESS;
}
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