python kmp算法

求模板串的最长前缀后缀公共串

def compute_lps_array(pattern: str, lps: list):
    """
    计算lps数组，即对应字符串的最长前缀和最长后缀的长度
    """
    j = 0
    lps[0] = 0
    for i in range(1, len(pattern)):
        if pattern[i] == pattern[j]:
            j += 1
            lps[i] = j
        else:
            j = 0
            lps[i] = 0

求模板串在text中的索引

def kmp_search(text: str, pattern: str) -> int:
    """
    使用KMP算法在文本中查找模式字符串的位置
    """
    lps = [0] * len(pattern)
    compute_lps_array(pattern, lps)
    print(lps)
    i = 0
    j = 0
    while i < len(text):
        print(text[i],pattern[j])
        if text[i] == pattern[j]:
            i += 1
            j += 1
        elif j > 0:
            j = lps[j - 1]
        else:
            i += 1

        if j == len(pattern):
            return i - j
    return -1

kmp算法链接：
算法数据结构——字符串匹配算法KMP精讲及python实现