单因数三元组

/*
 * LeetCode 2198: Number of Single-Factor Triplets using Java Streams
 * Given an array of positive integers nums, find the number of triplets (i, j, k)
 * such that 0 <= i < j < k < nums.length and nums[i] * nums[j] * nums[k] is a multiple of nums[i], nums[j], and nums[k].
 * 
 * Approach:
 * - Use Java Streams to generate a stream of indices, and for each combination of three indices, check the divisibility condition.
 */
import java.util.stream.IntStream;

public class SingleFactorTripletsStream {
    public long countSingleFactorTriplets(int[] nums) {
        int n = nums.length;
        return IntStream.range(0, n - 2)
                .boxed()
                .flatMap(i -> IntStream.range(i + 1, n - 1)
                        .boxed()
                        .flatMap(j -> IntStream.range(j + 1, n)
                                .filter(k -> {
                                    int product = nums[i] * nums[j] * nums[k];
                                    return product % nums[i] == 0 && product % nums[j] == 0 && product % nums[k] == 0;
                                })
                                .mapToObj(k -> new int[]{i, j, k})
                        )
                )
                .count();
    }
}