unsigned has_same_digits(unsigned a, unsigned b)
{
unsigned digs = n_digits(a);
if (digs == n_digits(b)) {
unsigned digits[10] = {0};
unsigned i;
for (i=0;i<digs;i++)
digits[nth_digit(a,i)]++;
for (i=0;i<digs;i++) {
if (digits[nth_digit(b,i)] == 0)
return 0;
}
return 1;
}
return 0;
}
/*
Returns true if sequence reaches 89. Caches answers for efficiency
*/
bool reaches_89(long num)
{
if(num == 1) return false;
if(num == 89) return true;
if(num < CACHE_LIMIT && cache[num] != -1) return (cache[num] == 1) ? true : false;
char num_s[n_digits(num)+1];
sprintf(num_s, "%ld", num);
long square_sum = 0;
for(int i = 0; i < n_digits(num); i++)
{
int digit = num_s[i] - '0';
square_sum += digit*digit;
}
//printf("-> %ld ", square_sum);
bool ans = reaches_89(square_sum);
if(num < CACHE_LIMIT)
{
cache[num] = ans;
}
return ans;
}
/*
Returns true if and only if the number is pandigital
*/
bool is_pandigital(long long num)
{
int digits = n_digits(num);
//there can't exist a 10-digit or greater pandigital number
if(digits > 9) return false;
char num_s[digits + 1];
sprintf(num_s, "%lld", num);
//the index 0 is true because the number can't contain a 0 digit
bool digit_used[] = {true, false, false, false, false, false, false, false, false, false};
for(int i = 0; i < digits; i++)
{
int curr_digit = num_s[i] - '0';
if(digit_used[curr_digit] || curr_digit > digits)
{
return false;
}
digit_used[curr_digit] = true;
}
return true;
}
int main(void)
{
unsigned i,c = 0;
for (i=2;i<1000000;i++) {
if (is_prime(i)) {
unsigned len = n_digits(i);
unsigned char discard = 0;
unsigned j,tmp = i;
for (j=1;j<len;j++) {
tmp = (tmp/10) + (tmp%10) * ceil(pow(10,floor(log10(tmp))));
if (is_prime(tmp) == 0) {
discard = 1;
break;
}
}
if (discard==0)
c++;
}
}
printf("%u\n",c);
return 0;
}
