是否有一种有效的方法来检测字符串是否包含一大组特征字符串中的 substring？

Question

For example, given a string aaaaaaaaaXyz , I want to find out if it contains a substring which is in a characteristic string set {'xy','xyz','zzz','cccc','dddd',....} , which may have one million members. Is there an efficient way?

Answer 1

Given that your search set might be very large, I would recommend just iterating that set and checking for a potential substring match:

public boolean containsSubstring(String input, Set<String> subs) {
    boolean match = false;

    for (String sub : subs) {
        if (input.contains(sub)) {
            match = true;
            break;
        }
    }

    return match;
}

Answer 2

First of all, you prepare the dictionary . just like this

Set<String> stringSet = Set.of("xy", "xyz", "zzz", "zzy", "cccc", "dddd");
Map<Character, List<String>> dictionary = new HashMap<>();
for (String word : stringSet)
    dictionary.computeIfAbsent(word.charAt(0), k -> new ArrayList<>()).add(word);
System.out.println(dictionary);

output:

{c=[cccc], d=[dddd], x=[xyz, xy], z=[zzy, zzz]}

And you can use this method to find out.

static boolean contains(String input, Map<Character, List<String>> dictionary) {
    for (int i = 0, max = input.length(); i < max; ++i) {
        char first = input.charAt(i);
        if (dictionary.containsKey(first))
            for (String word : dictionary.get(first))
                if (input.startsWith(word, i))
                    return true;
    }
    return false;
}

Answer 3

With the hint of Clashsoft ,I found the java implementation of Aho-Corasick algorithm, which is the one i want,thanks for Clashsoft