2020数据结构小学期（一）——KMP匹配算法

1、  KMP模式匹配算法

输入：模式串，主串

功能要求：输出模式串的next值表，输出匹配结果

源码：

def matchintg_KMP(t, p, prefix):
    n, m = len(t), len(p)
    j, i = 0, 0
    while j < n and i < m:
        if i == -1 or t[j] == p[i]:
            i, j = i + 1, j + 1
        else:
            i = prefix[i]
    if i == m:
        return j - i
    return -1


def prefix_table(p):
    i, k, m = 0, -1, len(p)
    prefix = [-1] * m
    while i < m - 1:
        if k == -1 or p[i] == p[k]:
            i, k = i + 1, k + 1
            if p[i] == p[k]:
                prefix[i] = prefix[k]
            else:
                prefix[i] = k
        else:
            k = prefix[k]
    return prefix


if __name__ == '__main__':
    # t = "ababcabcacbab"
    # p = "abcac"
    t = input("请输入主串：")
    p = input("请输入模式串：")
    pnext = prefix_table(p)
    print("模式串next表：", pnext)
    print("匹配结果：", matchintg_KMP(t, p, pnext))