kpm算法基本操作代码实现

以下是 KMP 算法的基本操作代码实现：

def kmp(text, pattern):
    n = len(text)
    m = len(pattern)
    if m == 0:
        return 0
    fail = compute_fail(pattern)
    j = 0
    for i in range(n):
        while j > 0 and pattern[j] != text[i]:
            j = fail[j-1]
        if pattern[j] == text[i]:
            j += 1
        if j == m:
            return i - m + 1
    return -1

def compute_fail(pattern):
    m = len(pattern)
    fail = [0] * m
    j = 0
    for i in range(1, m):
        while j > 0 and pattern[j] != pattern[i]:
            j = fail[j-1]
        if pattern[j] == pattern[i]:
            j += 1
        fail[i] = j
    return fail

这段代码实现了 KMP 算法的主要逻辑，其中 `compute_fail` 函数用于计算模式串的失配函数，`kmp` 函数用于在文本串中查找模式串。