092.c


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const int limit = 10000000;

const int squares[10] = { 0, 1, 4, 9, 16, 25, 36, 49, 64, 81 };

int next_chain(int number)
{
	int sum = 0;
	int digit;
	while(number > 0)
	{
		digit = number % 10;
		number = number / 10;
		sum += squares[digit];
	}
	return sum;
}

int main()
{
	int* numbers = calloc(limit, sizeof(int));
	int i, count;

	for(i=0; i<limit; i++)
		numbers[i] = next_chain(i);

	count = 0;

	for(i=1; i<limit; i++)
	{
		int next = numbers[i];
		while(next != 1 && next != 89)
			next = numbers[next];

		numbers[i] = next;
		if(next == 89)
			count++;
	}

	printf("%d\n", count);

	return 0;
}