用于模式搜索的 KMP 算法的Python程序
Python
# Python program for KMP Algorithm
def KMPSearch(pat, txt):
M = len(pat)
N = len(txt)
# create lps[] that will hold the longest prefix suffix
# values for pattern
lps = [0]*M
j = 0 # index for pat[]
# Preprocess the pattern (calculate lps[] array)
computeLPSArray(pat, M, lps)
i = 0 # index for txt[]
while i < N:
if pat[j] == txt[i]:
i += 1
j += 1
if j == M:
print "Found pattern at index " + str(i-j)
j = lps[j-1]
# mismatch after j matches
elif i < N and pat[j] != txt[i]:
# Do not match lps[0..lps[j-1]] characters,
# they will match anyway
if j != 0:
j = lps[j-1]
else:
i += 1
def computeLPSArray(pat, M, lps):
len = 0 # length of the previous longest prefix suffix
lps[0] # lps[0] is always 0
i = 1
# the loop calculates lps[i] for i = 1 to M-1
while i < M:
if pat[i]== pat[len]:
len += 1
lps[i] = len
i += 1
else:
# This is tricky. Consider the example.
# AAACAAAA and i = 7. The idea is similar
# to search step.
if len != 0:
len = lps[len-1]
# Also, note that we do not increment i here
else:
lps[i] = 0
i += 1
txt = "ABABDABACDABABCABAB"
pat = "ABABCABAB"
KMPSearch(pat, txt)
# This code is contributed by Bhavya Jain
有关更多详细信息,请参阅关于模式搜索的 KMP 算法的完整文章!
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