1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
|
#pragma once
#include <util/draft/matrix.h>
#include <util/generic/algorithm.h>
#include <util/generic/vector.h>
#include <util/system/yassert.h>
#include <type_traits>
#include <utility>
namespace NLevenshtein {
enum EEditMoveType {
EMT_SPECIAL,
EMT_PRESERVE,
EMT_REPLACE,
EMT_DELETE,
EMT_INSERT
};
inline bool IsImportantEditMove(EEditMoveType p) {
return (p != EMT_SPECIAL && p != EMT_PRESERVE);
}
inline void MakeMove(EEditMoveType t, int& p1, int& p2) {
switch (t) {
case EMT_PRESERVE:
case EMT_REPLACE:
p1++;
p2++;
break;
case EMT_DELETE:
p1++;
break;
case EMT_INSERT:
p2++;
break;
default:
break;
}
}
using TEditChain = TVector<EEditMoveType>;
template <typename TArgType>
struct TWeightOneUnaryGetter {
int operator()(const TArgType&) const {
return 1;
}
};
template <typename TArgType>
struct TWeightOneBinaryGetter {
int operator()(const TArgType&, const TArgType&) const {
return 1;
}
};
template <typename TStringType>
using TCharType = typename std::decay_t<decltype(std::add_const_t<TStringType>()[0])>;
/// Finds sequence of "edit moves" for two strings
template <class TStringType, class TWeightType = int,
class TReplaceWeigher = TWeightOneBinaryGetter<TCharType<TStringType>>,
class TDeleteWeigher = TWeightOneUnaryGetter<TCharType<TStringType>>,
class TInsertWeigher = TWeightOneUnaryGetter<TCharType<TStringType>>
>
void GetEditChain(const TStringType& str1, const TStringType& str2, TEditChain& res, TWeightType* weight = nullptr,
const TReplaceWeigher& replaceWeigher = TReplaceWeigher(),
const TDeleteWeigher& deleteWeigher = TDeleteWeigher(),
const TInsertWeigher& insertWeigher = TInsertWeigher())
{
int l1 = (int)str1.size();
int l2 = (int)str2.size();
TMatrix<std::pair<TWeightType, EEditMoveType>> ma(l1 + 1, l2 + 1); /// ma[i][j].first = diff(str1[0..i-1], str2[0..j-1])
ma[0][0] = std::make_pair(0, EMT_SPECIAL); // starting point
for (int i = 1; i <= l1; i++) {
ma[i][0] = std::make_pair(ma[i - 1][0].first + deleteWeigher(str1[i - 1]), EMT_DELETE);
}
for (int i = 1; i <= l2; i++) {
ma[0][i] = std::make_pair(ma[0][i - 1].first + insertWeigher(str2[i - 1]), EMT_INSERT);
}
// Here goes basic Levestein's algorithm
for (int i = 1; i <= l1; i++) {
for (int j = 1; j <= l2; j++) {
if (str1[i - 1] == str2[j - 1]) {
ma[i][j] = std::make_pair(ma[i - 1][j - 1].first, EMT_PRESERVE);
} else {
const TWeightType replaceWeight = replaceWeigher(str1[i - 1], str2[j - 1]);
Y_ASSERT(replaceWeight >= 0);
ma[i][j] = std::make_pair(ma[i - 1][j - 1].first + replaceWeight, EMT_REPLACE);
}
if (ma[i][j].first > ma[i - 1][j].first) {
const TWeightType deleteWeight = deleteWeigher(str1[i - 1]);
Y_ASSERT(deleteWeight >= 0);
const TWeightType deletePathWeight = ma[i - 1][j].first + deleteWeight;
if (deletePathWeight <= ma[i][j].first) {
ma[i][j] = std::make_pair(deletePathWeight, EMT_DELETE);
}
}
if (ma[i][j].first > ma[i][j - 1].first) {
const TWeightType insertWeight = insertWeigher(str2[j - 1]);
Y_ASSERT(insertWeight >= 0);
const TWeightType insertPathWeight = ma[i][j - 1].first + insertWeight;
if (insertPathWeight <= ma[i][j].first) {
ma[i][j] = std::make_pair(insertPathWeight, EMT_INSERT);
}
}
}
}
// Tracing the path from final point
res.clear();
res.reserve(Max<size_t>(l1, l2));
for (int i = l1, j = l2; ma[i][j].second != EMT_SPECIAL;) {
res.push_back(ma[i][j].second);
switch (ma[i][j].second) {
case EMT_PRESERVE:
case EMT_REPLACE:
--i;
--j;
break;
case EMT_DELETE:
--i;
break;
case EMT_INSERT:
--j;
break;
default:
// TODO: throw exception
break;
}
}
std::reverse(res.begin(), res.end());
if (weight != nullptr) {
*weight = ma[l1][l2].first;
}
}
template <class TStringType>
size_t Distance(const TStringType& str1, const TStringType& str2) {
TEditChain editChain;
GetEditChain(str1, str2, editChain);
size_t result = 0;
for (auto edit : editChain) {
if (IsImportantEditMove(edit))
result++;
}
return result;
}
/// Calculates substrings to be replaced for str1->str2 transformation
struct TReplacement {
int CorrectOffset, CorrectLength, MisspelledOffset, MisspelledLength;
TReplacement()
: CorrectOffset(0)
, CorrectLength(0)
, MisspelledOffset(0)
, MisspelledLength(0)
{
}
TReplacement(int correctOffset, int correctLength, int misspelledOffset, int misspelledLength)
: CorrectOffset(correctOffset)
, CorrectLength(correctLength)
, MisspelledOffset(misspelledOffset)
, MisspelledLength(misspelledLength)
{
}
};
template <class TStringType>
void GetStringReplacements(const TStringType& str1, const TStringType& str2, TVector<TReplacement>& res) {
TEditChain editChain;
GetEditChain(str1, str2, editChain);
editChain.push_back(EMT_SPECIAL);
int c1 = 0, c2 = 0;
res.clear();
for (TEditChain::const_iterator it = editChain.begin(); it != editChain.end(); it++) {
if (IsImportantEditMove(*it)) {
int sc1 = c1, sc2 = c2;
do {
MakeMove(*it, c1, c2);
++it;
} while (IsImportantEditMove(*it));
res.push_back(TReplacement(sc1, c1 - sc1, sc2, c2 - sc2));
}
MakeMove(*it, c1, c2);
}
}
}
|
