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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
typedef struct node {
int id;
bool end;
} node;
typedef struct connection {
node *parrent;
char input;
char output;
int offset;
node *result;
} connection;
node nodes[128];
int nodecount = 0;
connection connections[1024];
int connectioncount = 0;
void perror(const char *msg) {
fprintf(stderr, "%s\n", msg);
exit(1);
}
node *findnode(int id) {
for (int i = 0; i < nodecount; i++)
if (nodes[i].id == id) return &nodes[i];
return NULL;
}
int main(int argc, char **argv) {
if (argc <= 1) perror("no file given");
FILE *f = fopen(argv[1], "r");
if (f == NULL) perror("failed to open file");
/* define nodes */
char *line = malloc(128);
while (fgets(line, 128, f)[0] == '#') continue; /* handles comments */
char *tok = strtok(line, " ");
while (tok != NULL) {
if (tok[0] == 'e') {
nodes[nodecount].end = true;
tok++;
}
nodes[nodecount].id = atoi(tok);
nodecount++;
tok = strtok(NULL, " ");
}
/* define connections */
node *parrent, *result;
comment:
while (fgets(line, 128, f) != NULL) {
if (line[0] == '#' || line[0] == '\n') goto comment;
char *tok = strtok(line, " ");
if ((parrent = findnode(atoi(tok))) == NULL) perror("unknown node specified");
connections[connectioncount].parrent = parrent;
tok = strtok(NULL, " ");
if (tok[0] == '#') connections[connectioncount].input = 0;
else connections[connectioncount].input = tok[0];
tok = strtok(NULL, " ");
if (tok[0] == '#') connections[connectioncount].output = 0;
else connections[connectioncount].output = tok[0];
tok = strtok(NULL, " ");
connections[connectioncount].offset = atoi(tok);
tok = strtok(NULL, " ");
if ((result = findnode(atoi(tok))) == NULL) perror("unknown node specified");
connections[connectioncount].result = result;
connectioncount++;
}
char tape[4096] = {0};
if (argc >= 3) strcat(tape, argv[2]); /* fill the tape with user input, if they give it */
char *head = tape;
node *current = &nodes[0];
for (;;) {
success:
for (int i = 0; i < connectioncount; i++) {
if (connections[i].parrent == current && connections[i].input == *head){
*head = connections[i].output;
current = connections[i].result;
head += connections[i].offset;
goto success;
}
}
printf("%s\n", tape);
printf("%s\n", (current->end) ? "accept" : "reject"); /* did it end in a valid location */
break;
}
return 0;
}
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