KMP匹配算法

KMP匹配算法，

原理参考http://www.ruanyifeng.com/blog/2013/05/Knuth%E2%80%93Morris%E2%80%93Pratt_algorithm.html

 

难点在于next数组的求解。

 

参考算法导论的思路求解next数组：

详见http://www.cnblogs.com/c-cloud/p/3224788.html

然后用Python实现了一下。

def makeNext(parttenString):
    next = []
    m = len(parttenString)
    k = 0
    next.append(0)
    p = 1
    while p < m:
        while k > 0 and parttenString[k] != parttenString[p]:
            k = next[k - 1]
        if parttenString[k] == parttenString[p]:
            k += 1

        next.append(k)
        p += 1
    print "nextval = ",next
    return next

def KMPAlgorithm(parttenString,rawString):
    nextval = makeNext(parttenString)
    isContain = False
    locationInRawString = 0
    locationInparttenString = 0
    lengthOfPartten = len(parttenString)
    lengthOfrawString = len(rawString)
    print lengthOfrawString,lengthOfPartten
    sameChar = 0
    while isContain == False:
        print locationInRawString,locationInparttenString
        while locationInparttenString < lengthOfPartten and locationInRawString < lengthOfrawString and parttenString[locationInparttenString] == rawString[locationInRawString]:
            if locationInparttenString == lengthOfPartten - 1:
                isContain = True
                break
            else:
                locationInRawString += 1
                locationInparttenString += 1
                sameChar += 1
        if lengthOfPartten - 1 == locationInparttenString and locationInRawString != lengthOfrawString - 1:
            break
        elif parttenString[locationInparttenString] != rawString[locationInRawString]:
            locationInRawString += 1
        else:
            locationInparttenString = locationInparttenString - (sameChar - nextval[locationInparttenString - 1])
            sameChar = 0
            if locationInRawString >= lengthOfrawString:
                break
    return isContain

if __name__ == "__main__":
    print KMPAlgorithm('CDAA','ABCDABCD')