用KMP算法求子串在主串中出现的次数

好的，以下是使用KMP算法求子串在主串中出现的次数的代码实现：

def KMPSearch(pat, txt):
    M = len(pat)
    N = len(txt)

    lps = [0]*M
    j = 0

    computeLPSArray(pat, M, lps)

    i = 0
    res = 0

    while i < N:
        if pat[j] == txt[i]:
            i += 1
            j += 1

        if j == M:
            res += 1
            j = lps[j-1]

        elif i < N and pat[j] != txt[i]:
            if j != 0:
                j = lps[j-1]
            else:
                i += 1

    return res


def computeLPSArray(pat, M, lps):
    len = 0

    lps[0] = 0
    i = 1

    while i < M:
        if pat[i] == pat[len]:
            len += 1
            lps[i] = len
            i += 1
        else:
            if len != 0:
                len = lps[len-1]
            else:
                lps[i] = 0
                i += 1

其中，`pat`是要查找的子串，`txt`是主串。函数`KMPSearch`返回子串在主串中出现的次数。