连续差相同的数字

// Java Stream solution

/*
 * Solution Approach using Java Streams:
 * 1. Similar recursive approach as the regular Java solution but with Streams.
 * 2. Use IntStream to iterate through possible starting digits.
 * 3. Use recursive stream generation to build numbers.
 * 4. Collect the results into a list.
 */

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class SolutionStream {
    public List<Integer> numsSameConsecDiff(int n, int k) {
        return IntStream.range(1, 10)
                .boxed()
                .flatMap(i -> findNumbersStream(i, n - 1, k))
                .collect(Collectors.toList());
    }

    private Stream<Integer> findNumbersStream(int currentNumber, int remainingDigits, int k) {
        if (remainingDigits == 0) return Stream.of(currentNumber);
        int lastDigit = currentNumber % 10;
        return Stream.concat(
                (lastDigit + k <= 9 ? findNumbersStream(currentNumber * 10 + (lastDigit + k), remainingDigits - 1, k) : Stream.empty()),
                (k != 0 && lastDigit - k >= 0 ? findNumbersStream(currentNumber * 10 + (lastDigit - k), remainingDigits - 1, k) : Stream.empty())
        );
    }
}