Flow Python-string KMP match

First, let's look at a simple string match.

you can put the text string s fixed, the pattern string p from the S-aligned left edge, as the bearing part is exactly the same, the match succeeds, the failure will be the pattern string p overall to the right 1 locations, continue to check the Alignment section, repeat .

#朴素匹配def Naive_match (S, p):    m = Len (s), n = Len (p) for    I in range (m-n+1): #起始指针i        if s[i:i+n] = = P:            return T Rue    return False

About the KMP algorithm, the best is the Nanyi of the string matching KMP algorithm; read it all the way.
The truth is, preprocessing the pattern string p to get a partial matching table of the prefix, so that we can use the known information to figure out how many bits can be shifted to the right. that is, KMP = simple match + Mobile multi-bit.
A lot of other details please see Nanyi's article, this will not unfold.
The following is a Python code implementation.

#KMPdef Kmp_match (S, p):    m = Len (s), n = Len (p)    cur = 0# start pointer cur    table = partial_table (p) while    cur<=m-n : For        i in range (n):            if s[i+cur]!=p[i]:                cur + = max (i-table[i-1], 1) #有了部分匹配表, we are not just simple 1-bit 1-bit to move to the right, to move multiple bits at once                break        Else:            return True    return false# partial match table Def partial_table (p): "'    partial_table (" Abcdabd " ), [0, 0, 0, 0, 1, 2, 0] "    prefix = set ()    postfix = set ()    ret = [0] for    i in range (1,len (P)): 
   prefix.add (p[:i])        postfix = {p[j:i+1] for J in range (1,i+1)}        ret.append (Len ((Prefix&postfix or {'}). Pop ()))    return retprint naive_match ("BBC abcdab Abcdabcdabde", "Abcdabd") Print partial_table ("Abcdabd") print KMP _match ("BBC abcdab Abcdabcdabde", "ABCDABD")

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Flow Python-string KMP match