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suffix_array_lcp.py

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Putul Singh 2024-10-19 13:40:04 +05:30 committed by GitHub
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1 changed files with 17 additions and 5 deletions
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divide_and_conquer/suffix_array_lcp.py
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@ -1,5 +1,6 @@
#!/usr/bin/env python3 #!/usr/bin/env python3
import doctest
def build_suffix_array(s: str) -> list[int]: def build_suffix_array(s: str) -> list[int]:
""" """
@ -11,13 +12,16 @@ def build_suffix_array(s: str) -> list[int]:
Returns: Returns:
list[int]: The suffix array (a list of starting indices of list[int]: The suffix array (a list of starting indices of
suffixes in sorted order). suffixes in sorted order).
Examples:
>>> build_suffix_array("banana")
[5, 3, 1, 0, 4, 2]
""" """
suffixes = [(s[i:], i) for i in range(len(s))] suffixes = [(s[i:], i) for i in range(len(s))]
suffixes.sort() # Sort the suffixes lexicographically suffixes.sort() # Sort the suffixes lexicographically
suffix_array = [suffix[1] for suffix in suffixes] suffix_array = [suffix[1] for suffix in suffixes]
return suffix_array return suffix_array
def build_lcp_array(s: str, suffix_array: list[int]) -> list[int]: def build_lcp_array(s: str, suffix_array: list[int]) -> list[int]:
""" """
Build the LCP array for the given string and suffix array. Build the LCP array for the given string and suffix array.
@ -28,6 +32,11 @@ def build_lcp_array(s: str, suffix_array: list[int]) -> list[int]:
Returns: Returns:
list[int]: The LCP array. list[int]: The LCP array.
Examples:
>>> suffix_array = build_suffix_array("banana")
>>> build_lcp_array("banana", suffix_array)
[0, 1, 3, 0, 0, 2]
""" """
n = len(s) n = len(s)
rank = [0] * n rank = [0] * n
@ -49,7 +58,6 @@ def build_lcp_array(s: str, suffix_array: list[int]) -> list[int]:
h -= 1 # Decrease h for the next suffix h -= 1 # Decrease h for the next suffix
return lcp return lcp
# Example usage # Example usage
if __name__ == "__main__": if __name__ == "__main__":
s = "banana" s = "banana"
@ -62,6 +70,10 @@ if __name__ == "__main__":
print("\nLCP Array:") print("\nLCP Array:")
for i in range(1, len(lcp_array)): for i in range(1, len(lcp_array)):
print( lcp_info = (f"LCP between {s[suffix_array[i - 1]:]} and "
f"LCP between {s[suffix_array[i - 1]:]} and {s[suffix_array[i]]}: {lcp_array[i]}" f"{s[suffix_array[i]]}: {lcp_array[i]}")
) print(lcp_info)
# Run doctests
if __name__ == "__main__":
doctest.testmod()