Add Suffix Automaton algorithm in strings - #15082
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| occurrences = [0] * len(self.states) | ||
| order = sorted( | ||
| range(len(self.states)), | ||
| key=lambda i: self.states[i].length, |
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Pull request overview
This pull request adds a new string-processing algorithm module implementing a Suffix Automaton (SAM), enabling substring membership checks, distinct-substring counting, and substring occurrence counting over a fixed input string.
Changes:
- Add
strings/suffix_automaton.pyimplementing SAM construction and core query operations. - Include doctests demonstrating
contains,count_distinct_substrings,count_occurrences, and input validation for empty strings.
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| def __init__(self, string: str) -> None: | ||
| if not string: | ||
| raise ValueError("Input string must not be empty.") | ||
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| self.states: list[State] = [State(length=0, link=-1)] | ||
| self.last: int = 0 | ||
| self.string: str = string | ||
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| for char in string: | ||
| self.extend(char) | ||
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| def extend(self, char: str) -> None: | ||
| """ | ||
| Extend the Suffix Automaton by appending character char. | ||
| Time Complexity: O(1) amortized | ||
| """ | ||
| curr = len(self.states) | ||
| self.states.append(State(length=self.states[self.last].length + 1)) |
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| def count_occurrences(self, pattern: str) -> int: | ||
| """ | ||
| Count occurrences of pattern as a substring in the text in O(|pattern|) time. | ||
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| >>> sam = SuffixAutomaton("banana") | ||
| >>> sam.count_occurrences("an") | ||
| 2 | ||
| >>> sam.count_occurrences("na") | ||
| 2 | ||
| >>> sam.count_occurrences("banana") | ||
| 1 | ||
| >>> sam.count_occurrences("xyz") | ||
| 0 | ||
| """ |
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| occurrences = [0] * len(self.states) | ||
| order = sorted( | ||
| range(len(self.states)), | ||
| key=lambda i: self.states[i].length, |
There was a problem hiding this comment.
Please provide descriptive name for the parameter: i
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This is not the final commit |
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Describe your change:
This pull request implements the Suffix Automaton (SAM) data structure and algorithm in
strings/suffix_automaton.py.A Suffix Automaton is the minimal Deterministic Finite Automaton (DFA) that recognizes all suffixes and substrings of a given string in$O(N)$ time and $O(N)$ space.
Key features implemented:
contains).count_distinct_substrings).count_occurrences).Checklist: