113 lines
2.6 KiB
C++
113 lines
2.6 KiB
C++
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/*
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----
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This file is part of SECONDO.
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Copyright (C) 2015, University in Hagen, Department of Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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//paragraph [1] Title: [{\Large \bf \begin{center}] [\end{center}}]
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//paragraph [2] Filename: [{\tt \begin{center}] [\end{center}}]
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[1] Implementation of the Edit Distance (ED) Algorithm
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[2] EditDistanceAlgorithm.cpp
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\tableofcontents
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\noindent
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1 Introduction
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This file implements the Edit Distance algorithm.
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2 Includes
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*/
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#include "EditDistanceAlgorithm.h"
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#include <vector>
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namespace tsa {
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/*
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3 Implementation of Edit Distance algorithm
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Implementation of the Edit Distance algorithm as described in
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\cite[fig. 2]{M86}.
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*/
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size_t edit_distance(size_t m, size_t n, ed_match_t match)
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{
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return edit_distance(m, n, match, m + n);
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}
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ssize_t edit_distance(
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const size_t m, const size_t n, ed_match_t match, const size_t max)
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{
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/*
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The original algorithm uses an array with the index interval $[-max, max]$.
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Since C++ does not support negative indices, this implementation uses $max$ as
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offset to map indices to the range $[0, 2max]$.
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*/
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std::vector<size_t> v((2 * max) + 1);
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v[max + 1] = 0;
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for (ssize_t d = 0; d <= static_cast<ssize_t>(max); ++d) {
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for (ssize_t k = -d; k <= d; k += 2) {
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size_t x =
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((k == -d) || (k != d && v[max + k - 1] < v[max + k + 1])) ?
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v[max + k + 1] : v[max + k - 1] + 1;
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size_t y = x - k;
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while (x < m && y < n && match(x, y)) {
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++x; ++y;
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}
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if (x >= m && y >= n)
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return d;
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v[max + k] = x;
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}
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}
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/*
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This point is never reached, if $max \ge m+n$.
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*/
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return -1;
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}
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} //-- namespace tsa
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/*
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\begin{thebibliography}{ABCD99}
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//[Oe] [\"{O}]
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\bibitem[M86]{M86}
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Eugene W.\ Myers.
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\newblock {An {O(ND)} Difference Algorithm and Its Variations}.
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\newblock {\em Algorithmica}, 1(2): 251--266, 1986,
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http://dx.doi.org/10.1007/BF01840446;
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http://dblp.uni-trier.de/rec/bib/journals/algorithmica/Meyers86.
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\end{thebibliography}
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*/
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