adventofcodeday2.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>

typedef struct {
  u_long **lids;
  u_long sum;
} product_ids;

void init(product_ids *prod_ids) {
  prod_ids->lids = malloc(2 * sizeof(u_long *));
  for (int i = 0; i < 2; i++) {
    prod_ids->lids[i] = malloc(sizeof(u_long));
  }
  prod_ids->sum = 0;
}

void free_prod_ids(product_ids *prod_ids) {
  for (int i = 0; i < 2; i++) {
    free(prod_ids->lids[i]);
  }
  free(prod_ids->lids);
  free(prod_ids);
}

int check_id(char *id) {
  char *tmp = malloc(128);
  for (u_long i = 0; i < (u_long)(strlen(id) / 2); i++) {
    tmp[i] = id[i];
    tmp[i + 1] = '\0';
  }
  return strstr(id + strlen(id) / 2, tmp) != NULL;
}

void check_ids(product_ids *prod_ids) {
  char *id = malloc(128);
  for (u_long i = *prod_ids->lids[0]; i <= *prod_ids->lids[1]; i++) {
    sprintf(id, "%lu", i);
    if (strlen(id) % 2 == 0) {
      if (check_id(id)) {
        prod_ids->sum += i;
      };
    }
  }
}

int main() {
  /*
    char *s = "532525253252525325";
    printf("%lu\n", strtoul(s, NULL, 10));
  */
  product_ids *prod_ids = malloc(sizeof(product_ids));
  init(prod_ids);

  FILE *file = fopen("input", "r");
  if (file == NULL) {
    printf("Error opening file\n");
    return 1;
  }

  while (fscanf(file, "%lu-%lu", prod_ids->lids[0], prod_ids->lids[1])) {
    check_ids(prod_ids);
    int c = fgetc(file);
    if (c != 44) {
      break;
    }
    ungetc(c, file);
    fseek(file, 1, SEEK_CUR);
  }
  printf("Final sum is: %lu\n", prod_ids->sum);

  free_prod_ids(prod_ids);
  return 0;
}