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#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#define INPUT_LEN 650
struct Operation
{
char opcode;
int arg;
char has_been_executed;
};
int execute(struct Operation *ops, size_t opcount)
{
struct Operation *cur_op = ops;
int acc = 0;
do {
if (cur_op->has_been_executed) {
return -1;
}
cur_op->has_been_executed = 1;
switch (cur_op->opcode)
{
case 0:
cur_op++;
break;
case 1:
acc += cur_op->arg;
cur_op++;
break;
case 2:
cur_op += cur_op->arg;
break;
}
} while (cur_op < ops + opcount);
return acc;
}
int exe_program(const char *filename)
{
FILE *file = fopen(filename, "r");
// Include space for newline and string terminator
char buffer[16] = { 0 };
struct Operation *ops = malloc(INPUT_LEN * sizeof(struct Operation));
size_t opcount = 0;
while (fgets(buffer, 16, file)) {
struct Operation *op = &ops[opcount++];
op->has_been_executed = 0;
switch (buffer[0])
{
// nop
case 'n':
op->opcode = 0;
break;
// acc
case 'a':
op->opcode = 1;
break;
// jmp
case 'j':
op->opcode = 2;
break;
}
op->arg = atoi(&buffer[4]);
}
fclose(file);
struct Operation *cur_op = ops;
int flip_previous = 0;
do {
if (flip_previous) {
(cur_op - 1)->opcode ^= 2;
flip_previous = 0;
}
if (cur_op->opcode == 1
|| (cur_op->opcode == 0 && cur_op->arg <= 0)
|| (cur_op->opcode == 2 && cur_op->arg >= 0)) {
continue;
}
cur_op->opcode ^= 2;
flip_previous = 1;
for (size_t i = 0; i < opcount; i++) {
ops[i].has_been_executed = 0;
}
int acc = execute(ops, opcount);
if (acc != -1) {
return acc;
}
} while (++cur_op < ops + opcount);
return -1;
}
int main(int argc, char *argv[])
{
printf("%i\n", exe_program(argv[argc - 1]));
}
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