int main() {
int i, v, prev_v, c = 0;
for (i = 1; i < SIZE; i++) {
v = sum_square_digits(i);
while (v != 89 && v != 1) {
prev_v = v;
v = sum_square_digits(v);
}
if (v == 89) {
c++;
}
}
printf("%d\n", c);
return 0;
}
int main(void) {
unsigned int i=0,result=0, count=0;
for (i=1; i<=100000000; i++) {
// if not 1 or 89, start the iteration
if ((i != 1) || (i != 89)) {
result = sum_square_digits(i);
}
// otherwise we're done already
else {
result = i;
}
// while we haven't reached 1 or 89, keep iterating
while ((result != 1) && (result != 89)) {
result = sum_square_digits(result);
}
if (result == 89) {
count++;
}
}
std::cout << count << std::endl;
return 0;
}
// builds all combinations digits 0-9 of length len
// for each of these it will perform iterated digit squaring
// and for those which result in 89 add to a counter which is
// passed by pointer.
long choose_sum_and_count_89(int * got, int n_chosen, int len, int at, int max_types, int *count89)
{
int i;
long count = 0;
int digitcounts[10];
for (i=0; i < 10; i++) {
digitcounts[i]=0;
}
if (n_chosen == len) {
if (!got) return 1;
int sum=0;
for (i = 0; i < len; i++) {
int digit=digits[got[i]];
digitcounts[digit]++;
sum=sum + digit * digit;
}
if (sum == 0) {
return 1;
}
if ((sum != 1) && (sum != 89)) {
while ((sum != 1) && (sum != 89)) {
sum=sum_square_digits(sum);
}
}
if (sum == 89) {
int count_this_comb=factorial(len);
for (i=0; i<10; i++) {
count_this_comb/=factorial(digitcounts[i]);
}
(*count89)+=count_this_comb;
}
return 1;
}
for (i = at; i < max_types; i++) {
if (got) got[n_chosen] = i;
count += choose_sum_and_count_89(got, n_chosen + 1, len, i, max_types, count89);
}
return count;
}
uint64_t convergent(uint64_t start) {
while(start != 1 && start != 89) start = sum_square_digits(start);
return start;
}
