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- # Copyright (c) 2011 Google Inc. All rights reserved.
- #
- # Redistribution and use in source and binary forms, with or without
- # modification, are permitted provided that the following conditions are
- # met:
- #
- # * Redistributions of source code must retain the above copyright
- # notice, this list of conditions and the following disclaimer.
- # * Redistributions in binary form must reproduce the above
- # copyright notice, this list of conditions and the following disclaimer
- # in the documentation and/or other materials provided with the
- # distribution.
- # * Neither the name of Google Inc. nor the names of its
- # contributors may be used to endorse or promote products derived from
- # this software without specific prior written permission.
- #
- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- from array import array
- def edit_distance(str1, str2):
- unsignedShort = 'h'
- distances = [array(unsignedShort, (0,) * (len(str2) + 1)) for i in range(0, len(str1) + 1)]
- # distances[0][0] = 0 since distance between str1[:0] and str2[:0] is 0
- for i in range(1, len(str1) + 1):
- distances[i][0] = i # Distance between str1[:i] and str2[:0] is i
- for j in range(1, len(str2) + 1):
- distances[0][j] = j # Distance between str1[:0] and str2[:j] is j
- for i in range(0, len(str1)):
- for j in range(0, len(str2)):
- diff = 0 if str1[i] == str2[j] else 1
- # Deletion, Insertion, Identical / Replacement
- distances[i + 1][j + 1] = min(distances[i + 1][j] + 1, distances[i][j + 1] + 1, distances[i][j] + diff)
- return distances[len(str1)][len(str2)]
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