1019. Next Greater Node In Linked List

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public int[] nextLargerNodes(ListNode head) {
        List<Integer> nums = new ArrayList<>();
        for (; head != null; head = head.next) {
            nums.add(head.val);
        }
        Deque<Integer> stk = new ArrayDeque<>();
        int n = nums.size();
        int[] ans = new int[n];
        for (int i = n - 1; i >= 0; --i) {
            while (!stk.isEmpty() && stk.peek() <= nums.get(i)) {
                stk.pop();
            }
            if (!stk.isEmpty()) {
                ans[i] = stk.peek();
            }
            stk.push(nums.get(i));
        }
        return ans;
    }
}