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68 lines
1.8 KiB
Python
68 lines
1.8 KiB
Python
#!/usr/bin/env python3
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def build_suffix_array(s: str) -> list[int]:
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"""
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Build the suffix array for the given string.
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Parameters:
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s (str): The input string.
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Returns:
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list[int]: The suffix array (a list of starting indices of
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suffixes in sorted order).
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"""
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suffixes = [(s[i:], i) for i in range(len(s))]
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suffixes.sort() # Sort the suffixes lexicographically
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suffix_array = [suffix[1] for suffix in suffixes]
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return suffix_array
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def build_lcp_array(s: str, suffix_array: list[int]) -> list[int]:
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"""
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Build the LCP array for the given string and suffix array.
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Parameters:
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s (str): The input string.
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suffix_array (list[int]): The suffix array.
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Returns:
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list[int]: The LCP array.
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"""
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n = len(s)
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rank = [0] * n
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lcp = [0] * n
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# Compute the rank of each suffix
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for i, suffix_index in enumerate(suffix_array):
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rank[suffix_index] = i
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# Compute the LCP array
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h = 0
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for i in range(n):
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if rank[i] > 0:
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j = suffix_array[rank[i] - 1]
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while (i + h < n) and (j + h < n) and (s[i + h] == s[j + h]):
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h += 1
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lcp[rank[i]] = h
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if h > 0:
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h -= 1 # Decrease h for the next suffix
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return lcp
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# Example usage
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if __name__ == "__main__":
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s = "banana"
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suffix_array = build_suffix_array(s)
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lcp_array = build_lcp_array(s, suffix_array)
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print("Suffix Array:")
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for i in range(len(suffix_array)):
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print(f"{suffix_array[i]}: {s[suffix_array[i]:]}")
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print("\nLCP Array:")
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for i in range(1, len(lcp_array)):
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print(
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f"LCP between {s[suffix_array[i - 1]:]} and {s[suffix_array[i]]}: {lcp_array[i]}"
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)
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