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#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#define NUM_STACKS 9
struct stack {
char c;
struct stack *next;
};
struct stack *stacks[NUM_STACKS];
void
stack_init(unsigned n) {
/* NULL means bottom of the stack. */
stacks[n-1] = NULL;
}
char
stack_pop(unsigned n) {
char c;
struct stack *old;
if (stacks[n-1] == NULL) {
fprintf(stderr, "stack underflow!\n");
exit(1);
}
c = stacks[n-1]->c;
old = stacks[n-1];
stacks[n-1] = stacks[n-1]->next;
free(old);
return c;
}
void
stack_push(unsigned n, char c) {
struct stack *new = malloc(sizeof (struct stack));
if (new == NULL) {
perror("malloc");
exit(1);
}
new->c = c;
new->next = stacks[n-1];
stacks[n-1] = new;
}
void
stack_destroy(unsigned n) {
struct stack *j, *i = stacks[n-1];
while (i != NULL) {
j = i->next;
free(i);
i = j;
}
}
int
main(int argc, char **argv) {
char *buf = NULL;
size_t buflen = 0;
ssize_t n;
FILE *f;
for (int i = 1; i <= NUM_STACKS; i++)
stack_init(i);
if (argc != 2) {
fprintf(stderr, "usage: %s input\n", argv[0]);
return 1;
}
f = fopen(argv[1], "r");
if (f == NULL) {
perror(argv[1]);
return 1;
}
/* initialise stacks */
char inits[][9] = {
"QMGCL",
"RDLCTFHG",
"VJFNMTWR",
"JFDVQP",
"NFMSLBT",
"RNVHCDP",
"HCT",
"GSJVZNHP",
"ZFHG"};
for (unsigned i = 0; i < sizeof(inits)/sizeof(inits[0]); i++) {
for (int j = 0; inits[i][j] != '\0'; j++) {
stack_push(i+1, inits[i][j]);
}
}
while ((n = getline(&buf, &buflen, f)) != -1) {
if (buf[n - 1] == '\n') {
buf[n - 1] = '\0';
n--;
}
unsigned num_to_move, from, to;
int ret;
if ((ret = sscanf(buf, "move %u from %u to %u", &num_to_move, &from, &to)) != 3) {
fprintf(stderr, "couldn't parse line \"%s\"\n", buf);
free(buf);
exit(1);
}
else if (ret == EOF) {
perror("sscanf");
free(buf);
exit(1);
}
for (unsigned i = 0; i < num_to_move; i++) {
char c = stack_pop(from);
stack_push(to, c);
}
}
free(buf);
fclose(f);
for (int i = 1; i <= NUM_STACKS; i++) {
printf("%c", stacks[i-1]->c);
stack_destroy(i);
}
printf("\n");
return 0;
}
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