forked from OctaForge/libostd
use introsort for sorting
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@ -6,6 +6,8 @@
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#ifndef OCTA_ALGORITHM_H
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#define OCTA_ALGORITHM_H
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#include "math.h"
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#include "octa/functional.h"
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#include "octa/range.h"
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@ -43,30 +45,73 @@ namespace octa {
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namespace internal {
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template<typename T, typename U>
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struct UnaryCompare {
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T val;
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const T &val;
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U comp;
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bool operator()(const T &v) const { return comp(v, val); }
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};
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template<typename R, typename C>
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void quicksort(R range, C compare) {
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void hs_sift_down(R range, size_t s, size_t e, C compare) {
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size_t r = s;
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while ((r * 2 + 1) <= e) {
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size_t ch = r * 2 + 1;
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size_t sw = r;
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if (compare(range[sw], range[ch]))
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sw = ch;
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if (((ch + 1) <= e) && compare(range[sw], range[ch + 1]))
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sw = ch + 1;
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if (sw != r) {
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swap(range[r], range[sw]);
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r = sw;
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} else return;
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}
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}
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template<typename R, typename C>
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void heapsort(R range, C compare) {
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size_t len = range.length();
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size_t st = (len - 2) / 2;
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for (;;) {
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hs_sift_down(range, st, len - 1, compare);
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if (st-- == 0) break;
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}
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size_t e = len - 1;
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while (e > 0) {
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swap(range[e], range[0]);
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--e;
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hs_sift_down(range, 0, e, compare);
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}
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}
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template<typename R, typename C>
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void introloop(R range, C compare, size_t depth) {
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if (range.length() <= 10) {
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insertion_sort(range, compare);
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return;
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}
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if (depth == 0) {
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heapsort(range, compare);
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return;
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}
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typename RangeTraits<R>::reference p = range[range.length() / 2];
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swap(p, range.last());
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R r = partition(range, UnaryCompare<decltype(p), C>{ p, compare });
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R l = range.slice(0, range.length() - r.length());
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swap(r.first(), r.last());
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quicksort(l, compare);
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quicksort(r, compare);
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introloop(l, compare, depth - 1);
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introloop(r, compare, depth - 1);
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}
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template<typename R, typename C>
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void introsort(R range, C compare) {
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introloop(range, compare, size_t(2
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* (log(range.length()) / log(2))));
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}
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}
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template<typename R, typename C>
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void sort(R range, C compare) {
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internal::quicksort(range, compare);
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internal::introsort(range, compare);
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}
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template<typename R>
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