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Extend StringRef's edit-distance algorithm to permit an upper bound on the allowed edit distance

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116867 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Douglas Gregor
2010-10-19 22:13:48 +00:00
parent 8155ea4c3a
commit 5ee568ac27
2 changed files with 14 additions and 2 deletions
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9
lib/Support/StringRef.cpp
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@ -68,7 +68,8 @@ int StringRef::compare_numeric(StringRef RHS) const {
// Compute the edit distance between the two given strings.
unsigned StringRef::edit_distance(llvm::StringRef Other,
bool AllowReplacements) {
bool AllowReplacements,
unsigned MaxEditDistance) {
// The algorithm implemented below is the "classic"
// dynamic-programming algorithm for computing the Levenshtein
// distance, which is described here:
@ -94,6 +95,8 @@ unsigned StringRef::edit_distance(llvm::StringRef Other,
for (size_type y = 1; y <= m; ++y) {
current[0] = y;
unsigned BestThisRow = current[0];
for (size_type x = 1; x <= n; ++x) {
if (AllowReplacements) {
current[x] = min(previous[x-1] + ((*this)[y-1] == Other[x-1]? 0u:1u),
@ -103,8 +106,12 @@ unsigned StringRef::edit_distance(llvm::StringRef Other,
if ((*this)[y-1] == Other[x-1]) current[x] = previous[x-1];
else current[x] = min(current[x-1], previous[x]) + 1;
}
BestThisRow = min(BestThisRow, current[x]);
}
if (MaxEditDistance && BestThisRow > MaxEditDistance)
return MaxEditDistance + 1;
unsigned *tmp = current;
current = previous;
previous = tmp;