__int64 solve_125()
{
unsigned* buffer = new unsigned[SQRT_LIMIT + 1];
for(unsigned i = 1; i < SQRT_LIMIT; ++i)
buffer[i] = i * i;
std::set<unsigned> sqrtsum;
// 依次累加2个数,3个数...为一组的和.并判断是否是回文数,是的话加入set中.
for(unsigned len = 2; len <= SQRT_LIMIT; ++len)
{
unsigned tmp = std::accumulate(buffer + 1, buffer + len + 1, 0u);
if(tmp > LIMIT)
break;
if(ispandigital(tmp))
sqrtsum.insert(tmp);
for(unsigned j = 2; j <= SQRT_LIMIT; ++j)
{ // 例如序列abcd, Sum(a, b, c) = x, 那么Sum(b, c, d) = Sum(a, b, c) - a + d = Sum(a, b, c) + (d - a).
if((tmp += (buffer[j + len - 1] - buffer[j - 1])) > LIMIT)
break;
if(ispandigital(tmp))
sqrtsum.insert(tmp);
}
}
delete[] buffer;
return std::accumulate(sqrtsum.begin(), sqrtsum.end(), 0u);
}
int main() {
unsigned int v = 0;
size_t sum = 0;
for (size_t i = 0; i < MAX_RHS; ++i)
if (ispandigital(i))
sum += i;
printf("%lu\n", sum);
return 0;
}
int main(void)
{
char msg[200];
int start_tics, i, j, sq, max=0, count=0, primecnt=0, maxprime=1000000000;
char *sieve;
start_tics = clock();
/* Construct a sieve of Eratosthenes; our limit is a billion, since no */
/* pandigital number could have more than nine digits */
sieve = calloc(maxprime+1, /* allocate space for the sieve */
sizeof(char));
if (sieve == NULL)
err_exit("error: cannot allocate space for sieve[]!", 1);
sieve[0] = 0; /* 0 and 1 are not primes */
sieve[1] = 0;
for (i=2; i<=maxprime; i++) /* fill the rest of the sieve */
sieve[i] = 1; /* with ones */
sq = sqrt(maxprime);
for (i=0; i<=sq; i++) /* for each run of the loop, the first */
{ /* value of i with sieve[i] != 0 */
if (sieve[i] != 0) /* is the next prime number */
for (j=i*i; j<=maxprime; j+=i)/* so strike out all multiples */
sieve[j] = 0; /* of that prime starting with */
} /* its square (lower multiples */
/* were taken care of earlier) */
for (i=0; i<=maxprime; i++) /* count the primes we found */
if (sieve[i] != 0)
primecnt++;
sprintf(msg, "to build the sieve of primes up to %d containing %d primes",
maxprime, primecnt);
logcputime(start_tics, msg);
for (i=1; i<maxprime; i++) /* now search the primes for */
{ /* pandigital numbers */
if ( (sieve[i] != 0) && (ispandigital(i)) )
{
count++;
max = i; /* the latest found will be the max */
}
}
sprintf(msg, "there are %d pandigital primes, and the largest is: %d", count, max);
logcputime(start_tics, msg);
exit(0);
}
