环绕字符串中唯一的子字符串

/*
 * Problem statement:
 * Given a string `s`, find the number of unique non-empty substrings of `s` that also appear in an infinitely repeated sequence of the English alphabet, `base = "abcdefghijklmnopqrstuvwxyz"`.
 *
 * Approach using Java Streams:
 * 1. Use a HashSet to store unique valid substrings.
 * 2. Utilize IntStream to generate start and end indices for substrings.
 * 3. For each generated substring, verify its validity in the cyclic base string.
 * 4. Use the helper method `isInBase` to check validity and add to set if valid.
 * 5. Return the size of the set.
 */
 
import java.util.*;
import java.util.stream.IntStream;
 
public class SolutionStream {
    public int findSubstringInWraproundString(String s) {
        Set<String> uniqueSubstrings = new HashSet<>();
        int n = s.length();
 
        // Use IntStream to generate start and end indices
        IntStream.range(0, n).forEach(i ->
            IntStream.range(i + 1, n + 1).forEach(j -> {
                String sub = s.substring(i, j);
                if (isInBase(sub)) {
                    uniqueSubstrings.add(sub);
                }
            })
        );
 
        return uniqueSubstrings.size();
    }
 
    private boolean isInBase(String sub) {
        int len = sub.length();
        for (int i = 1; i < len; i++) {
            if ((sub.charAt(i) - sub.charAt(i - 1) + 26) % 26 != 1) {
                return false;
            }
        }
        return true;
    }
}