47 lines
959 B
Python
47 lines
959 B
Python
# Based on https://github.com/AllAlgorithms, python/algorithms/math/rabin_karp.py
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# Rabin Karp Algorithm in python using hash values
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def rabin_karp_search(pat: str, txt: str) -> list:
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assert len(pat) <= len(txt)
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# d is the number of characters in input alphabet
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d = 2560
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q = 101
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M = len(pat)
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N = len(txt)
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i = 0
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j = 0
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p = 0
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t = 0
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h = 1
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for i in range(M - 1):
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h = (h * d) % q
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for i in range(M):
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p = (d * p + ord(pat[i])) % q
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t = (d * t + ord(txt[i])) % q
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found_at_index = []
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for i in range(N - M + 1):
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if p == t:
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for j in range(M):
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if txt[i + j] != pat[j]:
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break
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j += 1
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if j == M:
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found_at_index.append(i)
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if i < N - M:
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t = (d * (t - ord(txt[i]) * h) + ord(txt[i + M])) % q
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if t < 0:
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t = t + q
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return found_at_index
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