和至少为 K 的最短子数组

/*
 * Approach: In Java Stream API, we cannot directly use it to maintain the sliding window or deque structures.
 * Therefore, we will outline the steps and implement them with standard Java collections while using Streams where possible.
 */
import java.util.*;
import java.util.stream.*;

public class ShortestSubarraySumStream {
    public int shortestSubarray(int[] nums, int k) {
        int n = nums.length;
        long[] prefixSums = new long[n + 1];
        IntStream.range(0, n).forEach(i -> prefixSums[i + 1] = prefixSums[i] + nums[i]);
        int[] result = {Integer.MAX_VALUE};
        Deque<Integer> deque = new LinkedList<>();
        IntStream.range(0, n + 1).forEach(i -> {
            while (!deque.isEmpty() && prefixSums[i] - prefixSums[deque.peekFirst()] >= k) {
                result[0] = Math.min(result[0], i - deque.pollFirst());
            }
            while (!deque.isEmpty() && prefixSums[i] <= prefixSums[deque.peekLast()]) {
                deque.pollLast();
            }
            deque.addLast(i);
        });
        return result[0] == Integer.MAX_VALUE ? -1 : result[0];
    }
}