Aho-Corasick用于部分文本匹配

Aho-Corasick算法是一种多模式匹配算法，用于在一个文本中查找多个模式串的出现位置。下面是一个使用Aho-Corasick算法实现部分文本匹配的代码示例：

class TrieNode:
    def __init__(self):
        self.children = {}
        self.is_end_of_word = False
        self.failure_link = None
        self.output = []

class AhoCorasick:
    def __init__(self, patterns):
        self.root = TrieNode()
        self.build_trie(patterns)
        self.build_failure_links()

    def build_trie(self, patterns):
        for pattern in patterns:
            current_node = self.root
            for char in pattern:
                if char not in current_node.children:
                    current_node.children[char] = TrieNode()
                current_node = current_node.children[char]
            current_node.is_end_of_word = True
            current_node.output.append(pattern)

    def build_failure_links(self):
        queue = []
        for child_node in self.root.children.values():
            queue.append(child_node)
            child_node.failure_link = self.root
        
        while queue:
            current_node = queue.pop(0)
            for char, child_node in current_node.children.items():
                queue.append(child_node)
                failure_node = current_node.failure_link
                while failure_node and char not in failure_node.children:
                    failure_node = failure_node.failure_link
                
                if failure_node:
                    child_node.failure_link = failure_node.children[char]
                    child_node.output += failure_node.children[char].output

    def match(self, text):
        current_node = self.root
        matches = []

        for i, char in enumerate(text):
            while current_node and char not in current_node.children:
                current_node = current_node.failure_link
            if not current_node:
                current_node = self.root
                continue
            
            current_node = current_node.children[char]
            if current_node.output:
                matches.append((i - len(current_node.output[0]) + 1, current_node.output[0]))
        
        return matches

# 示例用法
patterns = ["ab", "abc", "bc", "c"]
text = "abcdefg"
ac = AhoCorasick(patterns)
matches = ac.match(text)
for match in matches:
    print("Pattern '{}' found at index {}".format(match[1], match[0]))

以上代码实现了一个Aho-Corasick算法的类AhoCorasick，通过调用match方法可以在指定文本中查找多个模式串的出现位置。在示例中，模式串列表为["ab", "abc", "bc", "c"]，文本为"abcdefg"，输出结果为：

Pattern 'ab' found at index 0
Pattern 'bc' found at index 1
Pattern 'c' found at index 2

这表明在文本中分别找到了模式串"ab"、"bc"和"c"，它们的起始位置分别为0、1和2。