c34026b101
note: done using ```sh git grep -l "2010-2024 Google" | xargs sed -i 's/2010-2024 Google/2010-2025 Google/' ```
60 lines
2.2 KiB
C++
60 lines
2.2 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/duplicate_remover.h"
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#include <cstddef>
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#include <cstdint>
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#include "absl/log/check.h"
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#include "absl/types/span.h"
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namespace operations_research {
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size_t DenseIntDuplicateRemover::RemoveDuplicatesInternal(
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absl::Span<int> span) {
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// We use vector<uint8_t> because using vector<bool> would be potentially more
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// expensive: writing in vector<bool> involves a read+write, and here we're
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// directly writing.
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int num_unique_kept = -1;
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// Fast track for the leading portion without duplicates.
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while (++num_unique_kept < span.size()) {
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const int x = span[num_unique_kept];
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DCHECK_GE(x, 0);
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DCHECK_LT(x, tmp_mask_.size() * 8);
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// Bit #i = Bit #(i modulo 8) of Byte #(i / 8).
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const uint8_t mask = 1u << (x & 7); // Bit #(i modulo 8).
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const uint8_t byte = tmp_mask_[x >> 3]; // .. of Byte #(i / 8).
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if (mask & byte) break; // Already seen.
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tmp_mask_[x >> 3] = byte | mask;
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}
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// The next portion is exactly the same, except that now we have to shift
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// the elements that we're keeping, making it slightly slower.
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for (int i = num_unique_kept + 1; i < span.size(); ++i) {
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const int x = span[i];
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DCHECK_GE(x, 0);
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DCHECK_LT(x, tmp_mask_.size() * 8);
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const uint8_t mask = 1 << (x & 7);
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const uint8_t byte = tmp_mask_[x >> 3];
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if (mask & byte) continue; // Already seen.
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tmp_mask_[x >> 3] = mask | byte;
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span[num_unique_kept++] = x; // Keep x=[i], at its new (shifted) position.
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}
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span.remove_suffix(span.size() - num_unique_kept);
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// Clear the bit mask.
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for (int x : span) tmp_mask_[x >> 3] = 0;
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return num_unique_kept;
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}
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} // namespace operations_research
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