测试字符串是否为字符串列表中任何子字符串的有效方法

Question

I want to know the best way to compare a string to a list of strings. Here is the code I have in my mind, but it's clear that it's not good in terms of time complexity.

for (String large : list1) {
    for (String small : list2) {
        if (large.contains(small)) {
            // DO SOMETHING
        } else {
            // NOT FOR ME
        }
    }

    // FURTHER MANIPULATION OF STRING 
}

Both lists of strings can contain more than thousand values, so the worst case complexity can rise to 1000×1000×length which is a mess. I want to know the best way to perform the task of comparing a string with a list of strings, in the given scenario above.

Answer 1

You could just do this:

 for (String small : list2) {
    if (set1.contains(small)) {
        // DO SOMETHING
    } else {
        // NOT FOR ME
    }
}

set1 should be the larger list of String, and instead of keeping it as a List<String> , use a Set<String> or a HashSet<String>

Answer 2

Thanks to the first answer by sandeep. Here is the solution:

List<String> firstCollection = new ArrayList<>();
Set<String> secondCollection = new HashSet<>();

//POPULATE BOTH LISTS HERE.

for(String string: firstCollection){
    if(secondCollection.contains(string)){
        //YES, THE STRING IS THERE IN THE SECOND LIST
    }else{
        //NOPE, THE STRING IS NOT THERE IN THE SECOND LIST
    }
}

Answer 3

This is, unfortunately, a difficult and messy problem. It's because you're checking whether a small string is a substring of a bunch of large strings, instead of checking that the small string is equal to a bunch of large strings.

The best solution depends on exactly what problem you need to solve, but here is a reasonable first attempt:

In a temporary place, concatenate all the large strings together, then construct a suffix tree on this long concatenated string. With this structure, we should be able to find all the substring matches of any given small among all the large quickly.