def build_sp(P):
sp = [0 for x in P]
Z = fundamental_preprocess(P)
for j in range(len(P) - 1, 0, -1):
i = j + Z[j] - 1
sp[i] = Z[j]
return sp
def full_shift_table(S):
F = [0 for c in S]
Z = fundamental_preprocess(S)
longest = 0
for i, zv in enumerate(reversed(Z)):
longest = max(zv, longest) if zv == i+1 else longest
F[-i-1] = longest
return F
def good_suffix_table(S):
L = [-1 for c in S]
N = fundamental_preprocess(S[::-1]) # S[::-1] reverses S
N.reverse()
for j in range(0, len(S)-1):
i = len(S) - N[j]
if i != len(S):
L[i] = j
return L
def test_no_prefix_matches(self):
S = "abcdefgh"
expected = [8, 0, 0, 0, 0, 0, 0, 0]
self.assertEqual(expected, fundamental_preprocess(S))
def test_single_char(self):
self.assertEqual([1], fundamental_preprocess("a"))
def test_empty_string(self):
self.assertEqual([], fundamental_preprocess(""))
def test_character_repeated(self):
S = "aaaaaaaa"
expected = [8, 7, 6, 5, 4, 3, 2, 1]
self.assertEqual(expected, fundamental_preprocess(S))
def test_overlapping_prefix_match(self):
S = "aabaabaaba"
expected = [10, 1, 0, 7, 1, 0, 4, 1, 0, 1]
self.assertEqual(expected, fundamental_preprocess(S))
def test_multiple_prefix_match(self):
S = "aabaacaab"
expected = [9, 1, 0, 2, 1, 0, 3, 1, 0]
self.assertEqual(expected, fundamental_preprocess(S))
def test_single_prefix_match(self):
S = "abab"
expected = [4, 0, 2, 0]
self.assertEqual(expected, fundamental_preprocess(S))
def string_search(P, T):
if len(P) == 0 or len(T) < len(P):
return []
matches = []
# Preprocessing
N = fundamental_preprocess(T[::-1]) # S[::-1] reverses S
N.reverse()
R = bad_character_table(P)
L = good_suffix_table(P)
F = full_shift_table(P)
M = [-1 for c in T]
k = len(P) - 1 # Represents alignment of end of P relative to T
i = len(P) - 1 # Character to compare in P
h = k # Character to compare in T
match = False # Indicates whether an exact match has been found in this phase
mismatch = False # Indicates whether a mismatch has occurred
while k < len(T):
if M[h] == -1 or M[h] == 0 or N[i] == 0: # Phase case 1
#print 'Case 1'
if T[h] == P[i]:
if i == 0: # Case 1a
match = True
mismatch = False
else: # Case 1b
i -= 1
h -= 1
match = False
mismatch = False
else: # Case 1c
match = False
mismatch = True
elif (M[h] < N[i] and M[h] != -1) or (M[h] == N[i] and 0 < N[i] < i+1): # Case 2 & 5
#print 'Case 2 & 5'
i -= M[h]
h -= M[h]
match = False
mismatch = False
elif M[h] >= N[i] and N[i] == i+1 > 0: # Phase case 3
#print 'Case 3'
match = True
mismatch = False
elif M[h] > N[i] and N[i] < i+1: # Phase case 4
#print 'Case 4'
i -= N[i]
h -= N[i]
match = False
mismatch = True
if match:
matches.append(k - len(P) + 1)
M[k] = k - h
k += len(P)-F[1] if len(P) > 1 else 1
i = len(P) - 1
h = k
match = False
mismatch = False
if mismatch:
char_shift = i - R[alphabet_index(T[h])][i]
if i+1 == len(P): # Mismatch happened on first attempt
suffix_shift = 1
elif L[i+1] == -1: # Matched suffix does not appear anywhere in P
suffix_shift = len(P) - F[i+1]
else: # Matched suffix appears in P
suffix_shift = len(P) - L[i+1]
M[k] = k - h
k += max(char_shift, suffix_shift)
i = len(P) - 1
h = k
match = False
mismatch = False
return matches