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The Boyer-Moore algorithm is used for pattern matching, which means finding a pattern (like a word) within a text. It’s faster than other methods because it skips sections of the text instead of checking each character one by one. How It Works: Right-to-Left Comparison: It starts comparing the patteRead more
The Boyer-Moore algorithm is used for pattern matching, which means finding a pattern (like a word) within a text. It’s faster than other methods because it skips sections of the text instead of checking each character one by one.
How It Works:
- Right-to-Left Comparison: It starts comparing the pattern from the rightmost character, moving left. This helps in skipping more characters when a mismatch is found.
- Bad Character Rule: If a mismatch happens, it uses the bad character rule to skip ahead. It checks where the mismatched character appears in the pattern and moves the pattern accordingly.
- Good Suffix Rule: If parts of the pattern match but a mismatch happens later, the good suffix rule is used. It skips ahead by comparing the matched part with the rest of the pattern.
Optimization:
- Skips More Characters: By using these rules, it skips more characters compared to checking each one, making it faster.
- Efficient for Large Texts: It’s especially good for large texts and patterns.
Example:
If you’re looking for “needle” in “haystackneedle”, it quickly skips non-matching sections and focuses on possible matches, making the search faster.
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The Boyer-Moore algorithm is an efficient string-searching algorithm for finding a substring (pattern) within a main string (text). Developed by Robert S. Boyer and J Strother Moore in 1977, it optimizes pattern matching by utilizing two key heuristics: the Bad Character Rule and the Good Suffix RulRead more
The Boyer-Moore algorithm is an efficient string-searching algorithm for finding a substring (pattern) within a main string (text). Developed by Robert S. Boyer and J Strother Moore in 1977, it optimizes pattern matching by utilizing two key heuristics: the Bad Character Rule and the Good Suffix Rule.
**Bad Character Rule**: When a mismatch occurs, the algorithm shifts the pattern to align the bad character in the text with its last occurrence in the pattern. If the bad character is not in the pattern, the pattern is shifted past the bad character.
**Good Suffix Rule**: Upon a mismatch, this rule shifts the pattern to align the longest suffix of the matched portion with another occurrence of this suffix within the pattern. If no such suffix exists, the pattern is shifted entirely past the mismatched character.
The algorithm starts comparing from the end of the pattern, allowing it to skip large sections of text, especially when mismatches are frequent. Preprocessing the pattern to create bad character and good suffix tables helps determine optimal shifts during the search, reducing the number of comparisons.
For example, searching for “NEEDLE” in “FINDINAHAYSTACKNEEDLEINA” involves comparing from the end of “NEEDLE”, using the heuristics to shift the pattern efficiently, leading to faster pattern matching compared to checking each character sequentially.
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