c34026b101
note: done using ```sh git grep -l "2010-2024 Google" | xargs sed -i 's/2010-2024 Google/2010-2025 Google/' ```
111 lines
3.3 KiB
C++
111 lines
3.3 KiB
C++
// Copyright 2010-2025 Google LLC
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "ortools/algorithms/sparse_permutation.h"
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#include <algorithm>
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#include <string>
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#include <utility>
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#include <vector>
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#include "absl/strings/str_join.h"
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#include "absl/types/span.h"
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#include "ortools/base/logging.h"
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namespace operations_research {
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void SparsePermutation::RemoveCycles(absl::Span<const int> cycle_indices) {
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// TODO(user): make this a class member to avoid allocation if the complexity
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// becomes an issue. In this case, also optimize the loop below by not copying
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// the first cycles.
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std::vector<bool> should_be_deleted(NumCycles(), false);
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for (int i : cycle_indices) {
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DCHECK_GE(i, 0);
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DCHECK_LT(i, NumCycles());
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DCHECK(!should_be_deleted[i])
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<< "Duplicate index given to RemoveCycles(): " << i;
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should_be_deleted[i] = true;
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}
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int new_cycles_size = 0; // new index in cycles_
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int new_cycle_ends_size = 0; // new index in cycle_ends_
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int start = 0;
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for (int i = 0; i < NumCycles(); ++i) {
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const int end = cycle_ends_[i];
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if (!should_be_deleted[i]) {
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for (int j = start; j < end; ++j) {
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cycles_[new_cycles_size++] = cycles_[j];
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}
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cycle_ends_[new_cycle_ends_size++] = new_cycles_size;
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}
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start = end;
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}
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cycles_.resize(new_cycles_size);
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cycle_ends_.resize(new_cycle_ends_size);
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}
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std::string SparsePermutation::DebugString() const {
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DCHECK_EQ(cycles_.empty(), cycle_ends_.empty());
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if (!cycles_.empty()) DCHECK_EQ(cycles_.size(), cycle_ends_.back());
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std::vector<std::vector<int>> cycles;
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int start = 0;
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for (const int end : cycle_ends_) {
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// Find the minimum.
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int min_pos = start;
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for (int i = start + 1; i < end; ++i) {
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if (cycles_[i] < cycles_[min_pos]) min_pos = i;
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}
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std::vector<int> cycle;
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for (int i = min_pos; i < end; ++i) cycle.push_back(cycles_[i]);
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for (int i = start; i < min_pos; ++i) cycle.push_back(cycles_[i]);
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cycles.push_back(std::move(cycle));
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start = end;
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}
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std::sort(cycles.begin(), cycles.end());
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std::string out;
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for (const std::vector<int>& cycle : cycles) {
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if (!out.empty()) out += " ";
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out += "(";
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out += absl::StrJoin(cycle, " ");
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out += ")";
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}
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return out;
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}
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int SparsePermutation::Image(int element) const {
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for (int c = 0; c < NumCycles(); ++c) {
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int cur_element = LastElementInCycle(c);
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for (int image : Cycle(c)) {
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if (cur_element == element) {
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return image;
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}
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cur_element = image;
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}
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}
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return element;
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}
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int SparsePermutation::InverseImage(int element) const {
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for (int c = 0; c < NumCycles(); ++c) {
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int cur_element = LastElementInCycle(c);
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for (int image : Cycle(c)) {
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if (image == element) {
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return cur_element;
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}
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cur_element = image;
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}
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}
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return element;
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}
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} // namespace operations_research
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