Function sum_digits_squared

ch1-c-threads/happycoin.c:16–24

}

uint64_t sum_digits_squared(uint64_t num) {
  uint64_t total = 0;
  while (num > 0) {
    uint64_t num_mod_base = num % 10;
    total += num_mod_base * num_mod_base;
    num = num / 10;
  }
  return total;
}

bool is_happy(uint64_t num) {
  while (num != 1 && num != 4) {