Fallout-like password-guessing game in C.

fallout-passwords.c

/* szomon :] */

/*
 * Fallout-like password-guessing game.
 *
 * Copyright: Szymon Urbaś
 * Licensed under the BSD (2-clause) license.
 */

#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h>
#include <time.h>

#define ATTEMPTS 5

#define GODMODE 0
#define DEBUG 0

#define ARR_SIZE(a) (sizeof(a) / sizeof(*a))

int main(void)
{
  char *passwords[] = {
    /* works when passwords have different length
     * but that's actually a dumb thing to do. */
    "VIRAL",
    "DARED",
    "MINES",
    "PARTS",
    "LIKES",
    "HAREM",
    "THREW",
    "SORTS",
    "FARTS"
  };

  char input[256];
  char *password;

  unsigned count = 0;
  int attempts = ATTEMPTS;

  int occurrences[26] = { 0 };
  int seen[26] = { 0 };

  int n;
  char *i, *p;
  char **pp;
  char *lf, *cr;

  srand(time(NULL));

  /* pick a random password */
  password = passwords[rand() % ARR_SIZE(passwords)];

#if GODMODE
  printf("GODMODE: password is %s\n\n", password);
#endif

  /* print out the table with possible passwords */
  for (n = 0; n < (ARR_SIZE(passwords) & ~1); n += 2){
    printf(" 0x%08x %-7s", rand(), passwords[n + 0]);
    printf(" 0x%08x %s\n", rand(), passwords[n + 1]);
  }

  /* print the 'odd' password if there's any */
  if (ARR_SIZE(passwords) & 1){
    printf(" 0x%08x %s\n", rand(), passwords[ARR_SIZE(passwords) - 1]);
  }

  printf("\n");

  /* the actual guessing */
  do {
    /* zero-out */
    count = 0;
    memset(occurrences, 0, sizeof(occurrences));
    memset(seen, 0, sizeof(seen));

    /* print the number of attempts and the 'boxes' */
    printf("%u attempt%s left! ", attempts, attempts == 1 ? "" : "s");
    for (n = 0; n < attempts; n++) printf("#");
    printf("\n");

    /* print the prompt */
    printf(" > ");
    /* fetch the input */
    fgets(input, 256, stdin);

    /* chomp */
    if ((lf = strrchr(input, '\n'))) *lf = '\0';
    if ((cr = strrchr(input, '\r'))) *cr = '\0';

    /* count how many times each letter in the alphabet appears in the
     * password */
    for (p = password; *p != '\0'; p++){
      occurrences[tolower(*p) - 'a']++;
    }

    /* go over every character in the input.. */
    for (i = input; *i != '\0'; i++){
      /* ignore any non-alphabetic characters */
      if (!isalpha(*i))
        continue;

      /* go over every character in the password and see if there's a match */
      for (p = password; *p != '\0'; p++){
        unsigned idx = tolower(*i) - 'a';

        /* this bit is magic so I won't explain it */
        if ((seen[idx] < occurrences[idx]) && (tolower(*i) == tolower(*p))){
#if DEBUG
          printf("char '%c' in input is equal to char '%c' in password\n", *i, *p);
#endif
          seen[idx]++;
          count++;
          break;
        }
      }
    }

    if (strcmp(input, password)){
      printf("Incorrect! %u/%lu characters right\n", count, strlen(password));
    } else {
      printf("Exact match! +75XP\n");
      return 0;
    }
  } while (--attempts);

  if (!attempts){
    printf("You have been temporarily locked out! Contact your's system administrator!\n");
    return 1;
  }

  return 0;
}

/*
 * vi: ft=c:ts=2:sw=2:expandtab
 */