void shellsort(void *base,
size_t nel)
{
size_t wgap, i, j, k;
const size_t width = sizeof(Element);
char tmp;
if ((nel > 1) && (width > 0)) {
assert(nel <= ((size_t)(-1)) / width); /* check for overflow */
wgap = 0;
do {
wgap = 3 * wgap + 1;
} while (wgap < (nel-1)/3);
/* From the above, we know that either wgap == 1 < nel or */
/* ((wgap-1)/3 < (int) ((nel-1)/3) <= (nel-1)/3 ==> wgap < nel. */
wgap *= width; /* So this can not overflow if wnel doesn't. */
nel *= width; /* Convert nel to 'wnel' */
do {
i = wgap;
do {
j = i;
do {
register char *a;
register char *b;
j -= wgap;
a = j + ((char *)base);
b = a + wgap;
if (sort_comparator(a, b) <= 0) {
break;
}
k = width;
do {
tmp = *a;
*a++ = *b;
*b++ = tmp;
} while (--k);
} while (j >= wgap);
i += width;
} while (i < nel);
wgap = (wgap - width)/3;
} while (wgap);
}
}
vector<pair<DOMAIN_TYPE, DOMAIN_TYPE>> *map_aggregation::top_k(int k)
{
vector<pair<DOMAIN_TYPE, DOMAIN_TYPE>> pairs;
for (auto iter = data.begin(); iter != data.end(); ++iter)
{
pairs.push_back(*iter);
}
sort(pairs.begin(), pairs.end(), sort_comparator());
vector<pair<DOMAIN_TYPE, DOMAIN_TYPE>> *result = new vector<pair<DOMAIN_TYPE, DOMAIN_TYPE>>();
for (int i = 0; i < min(k, pairs.size()); ++i)
{
result->push_back(pairs[i]);
}
return result;
}
