Regex to search in an array of strings

Question

Consider the following strings in an array defined in Java

G1
G12
G1-G2
G23

If the user enters G1, then the program should return the index of G1 and G1-G2 - > [0, 2]
If the user enters G2, the program should return the index G1-G2 -> [2]
If the user enters G12, the program should return the index of G12 -> [1]
...

One easy way to do that is to tokenize each array element with '-' and then use equals() for each element. That means an O(n^2) algorithm. Is there a better way to use regular expressions so that in one loop, the program searches for the pattern and use '-' as delimiting character?

bvrakvs · Accepted Answer · 2017-04-28 08:22:40Z

Solution would be to use the following regex;

.*(?=\b{value}\b).*

so, for example if you wish to capture G1 with your requirements;

.*(?=\bG1\b).*

Where \b is being utilized, the anchor for the beginning or the end of a word, that is perfect for your requirement. More on word boundary anchor \b, here

in Java I have the following code to test;

static List<String> list = Arrays.asList("G1", "G12", "G1-G2", "G23");
public static void main(String[] args) throws Exception {
    new ArrayList<>(Arrays.asList("G1", "G12", "G2", "G23")).forEach(s -> func(s));
}

static void func(String input) {
    String regex = ".*(?=\\b" + input + "\\b).*";
    System.out.println(input + " contained in -> " 
                       + Arrays.toString(IntStream.range(0, list.size())
                                       .filter(i -> list.get(i).matches(regex))
                                       .toArray()));
}

which results in;

G1 contained in -> [0, 2]
G12 contained in -> [1]
G2 contained in -> [2]
G23 contained in -> [3]

To see the code in action, here

Collectives™ on Stack Overflow

Regex to search in an array of strings

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related