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authorPaul Baltescu <pauldb89@gmail.com>2013-02-21 14:13:55 +0000
committerPaul Baltescu <pauldb89@gmail.com>2013-02-21 14:13:55 +0000
commitbca26d953a774b8efca12f30407390b3f5eef9d0 (patch)
treefe922de5c89b1844f677d550dcc24e87edd67a55 /klm/util/multi_intersection.hh
parent54a1c0e2bde259e3acc9c0a8ec8da3c7704e80ca (diff)
parent95c364f2cb002241c4a62bedb1c5ef6f1e9a7f22 (diff)
Merge branch 'master' of https://github.com/pauldb89/cdec
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+#ifndef UTIL_MULTI_INTERSECTION__
+#define UTIL_MULTI_INTERSECTION__
+
+#include <boost/optional.hpp>
+#include <boost/range/iterator_range.hpp>
+
+#include <algorithm>
+#include <functional>
+#include <vector>
+
+namespace util {
+
+namespace detail {
+template <class Range> struct RangeLessBySize : public std::binary_function<const Range &, const Range &, bool> {
+ bool operator()(const Range &left, const Range &right) const {
+ return left.size() < right.size();
+ }
+};
+
+/* Takes sets specified by their iterators and a boost::optional containing
+ * the lowest intersection if any. Each set must be sorted in increasing
+ * order. sets is changed to truncate the beginning of each sequence to the
+ * location of the match or an empty set. Precondition: sets is not empty
+ * since the intersection over null is the universe and this function does not
+ * know the universe.
+ */
+template <class Iterator, class Less> boost::optional<typename std::iterator_traits<Iterator>::value_type> FirstIntersectionSorted(std::vector<boost::iterator_range<Iterator> > &sets, const Less &less = std::less<typename std::iterator_traits<Iterator>::value_type>()) {
+ typedef std::vector<boost::iterator_range<Iterator> > Sets;
+ typedef typename std::iterator_traits<Iterator>::value_type Value;
+
+ assert(!sets.empty());
+
+ if (sets.front().empty()) return boost::optional<Value>();
+ // Possibly suboptimal to copy for general Value; makes unsigned int go slightly faster.
+ Value highest(sets.front().front());
+ for (typename Sets::iterator i(sets.begin()); i != sets.end(); ) {
+ i->advance_begin(std::lower_bound(i->begin(), i->end(), highest, less) - i->begin());
+ if (i->empty()) return boost::optional<Value>();
+ if (less(highest, i->front())) {
+ highest = i->front();
+ // start over
+ i = sets.begin();
+ } else {
+ ++i;
+ }
+ }
+ return boost::optional<Value>(highest);
+}
+
+} // namespace detail
+
+template <class Iterator, class Less> boost::optional<typename std::iterator_traits<Iterator>::value_type> FirstIntersection(std::vector<boost::iterator_range<Iterator> > &sets, const Less less) {
+ assert(!sets.empty());
+
+ std::sort(sets.begin(), sets.end(), detail::RangeLessBySize<boost::iterator_range<Iterator> >());
+ return detail::FirstIntersectionSorted(sets, less);
+}
+
+template <class Iterator> boost::optional<typename std::iterator_traits<Iterator>::value_type> FirstIntersection(std::vector<boost::iterator_range<Iterator> > &sets) {
+ return FirstIntersection(sets, std::less<typename std::iterator_traits<Iterator>::value_type>());
+}
+
+template <class Iterator, class Output, class Less> void AllIntersection(std::vector<boost::iterator_range<Iterator> > &sets, Output &out, const Less less) {
+ typedef typename std::iterator_traits<Iterator>::value_type Value;
+ assert(!sets.empty());
+
+ std::sort(sets.begin(), sets.end(), detail::RangeLessBySize<boost::iterator_range<Iterator> >());
+ boost::optional<Value> ret;
+ for (boost::optional<Value> ret; ret = detail::FirstIntersectionSorted(sets, less); sets.front().advance_begin(1)) {
+ out(*ret);
+ }
+}
+
+template <class Iterator, class Output> void AllIntersection(std::vector<boost::iterator_range<Iterator> > &sets, Output &out) {
+ AllIntersection(sets, out, std::less<typename std::iterator_traits<Iterator>::value_type>());
+}
+
+} // namespace util
+
+#endif // UTIL_MULTI_INTERSECTION__