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/**************************************************************************
* *
* Regina - A Normal Surface Theory Calculator *
* Computational Engine *
* *
* Copyright (c) 1999-2025, Ben Burton *
* For further details contact Ben Burton (bab@debian.org). *
* *
* This program is free software; you can redistribute it and/or *
* modify it under the terms of the GNU General Public License as *
* published by the Free Software Foundation; either version 2 of the *
* License, or (at your option) any later version. *
* *
* As an exception, when this program is distributed through (i) the *
* App Store by Apple Inc.; (ii) the Mac App Store by Apple Inc.; or *
* (iii) Google Play by Google Inc., then that store may impose any *
* digital rights management, device limits and/or redistribution *
* restrictions that are required by its terms of service. *
* *
* This program is distributed in the hope that it will be useful, but *
* WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
* General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program. If not, see <https://www.gnu.org/licenses/>. *
* *
**************************************************************************/
#include "link/link.h"
#include "triangulation/cut.h"
namespace regina {
bool Cut::isTrivial() const {
if (size_ == 0)
return true;
for (size_t i = 1; i < size_; ++i)
if (side_[i] != side_[0])
return false;
return true;
}
size_t Cut::weight(const Link& link) const {
if (link.size() != size_)
throw InvalidArgument("Cut::weight() requires a link diagram "
"with the same size as the cut.");
size_t ans = 0;
for (size_t i = 0; i < size_; ++i)
if (side(i) == 0) {
auto c = link.crossing(i);
for (int j = 0; j < 2; ++j) {
if (side_[c->next(j).crossing()->index()] == 1)
++ans;
if (side_[c->prev(j).crossing()->index()] == 1)
++ans;
}
}
return ans;
}
size_t Cut::weight(const ModelLinkGraph& graph) const {
if (graph.size() != size_)
throw InvalidArgument("Cut::weight() requires a model link graph "
"with the same size as the cut.");
size_t ans = 0;
for (size_t i = 0; i < size_; ++i)
if (side(i) == 0) {
auto n = graph.node(i);
for (int j = 0; j < 4; ++j) {
if (side_[n->adj(j).node()->index()] == 1)
++ans;
}
}
return ans;
}
bool Cut::inc() {
if (size_ == 0)
return false;
for (ssize_t pos = size_ - 1; pos >= 0; --pos) {
if (side_[pos] == 0) {
side_[pos] = 1;
return true;
} else
side_[pos] = 0;
}
return false;
}
void Cut::writeTextShort(std::ostream& out) const {
out << '(';
for (size_t i = 0; i < size_; ++i)
if (side_[i] == 0)
out << ' ' << i;
out << " |";
for (size_t i = 0; i < size_; ++i)
if (side_[i] == 1)
out << ' ' << i;
out << " )";
}
} // namespace regina
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