1019. Next Greater Node In Linked List

class Solution {
    private static class ListNodeWrapper {
        private final int value;
        private int nextLargerValue;

        public ListNodeWrapper(int value) {
            this.value = value;
        }
    }

    public int[] nextLargerNodes(ListNode head) {
        List<ListNodeWrapper> nodeList = new ArrayList<>();
        Stack<Integer> decreaseStack = new Stack<>(); // 非严格单调递减栈，栈中存储的为节点的索引

        ListNode curr = head;
        int index = 0;
        while (curr != null) {
            while (!decreaseStack.isEmpty() && curr.val > nodeList.get(decreaseStack.peek()).value) {
                // 出现了下一个更大的值
                ListNodeWrapper node = nodeList.get(decreaseStack.pop());
                node.nextLargerValue = curr.val;
            }

            nodeList.add(new ListNodeWrapper(curr.val));
            decreaseStack.push(index);
            index++;
            curr = curr.next;
        }

        int[] answers = new int[nodeList.size()];
        for (int i = 0; i < answers.length; i++) {
            answers[i] = nodeList.get(i).nextLargerValue;
        }
        return answers;
    }
}

References

1019. Next Greater Node In Linked List