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Fix Boyer-Moore bad character shift having no effect #15053

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Fix Boyer-Moore bad character shift having no effect #15053

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11 changes: 7 additions & 4 deletions strings/boyer_moore_search.py
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Original file line number Diff line number Diff line change
Expand Up @@ -86,15 +86,18 @@ def bad_character_heuristic(self) -> list[int]:
"""

positions = []
for i in range(self.textLen - self.patLen + 1):
i = 0
while i <= self.textLen - self.patLen:
mismatch_index = self.mismatch_in_text(i)
if mismatch_index == -1:
positions.append(i)
i += 1
else:
match_index = self.match_in_pattern(self.text[mismatch_index])
i = (
mismatch_index - match_index
) # shifting index lgtm [py/multiple-definition]
# shift pattern so the last occurrence of the mismatched
# character in the pattern aligns with the text, while
# always making at least one position of progress
i = max(i + 1, mismatch_index - match_index)
return positions


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