496. Next Greater Element I

class Solution {
    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
        int n = nums1.length, m = nums2.length;
        int[] res = new int[n];

        Deque<Integer> stack = new ArrayDeque<>();
        Map<Integer, Integer> map = new HashMap<>();

        for (int i = m - 1; i >= 0; i--) {
            while (!stack.isEmpty() && nums2[i] > nums2[stack.peek()]) {
                stack.pop();
            }

            map.put(nums2[i], stack.isEmpty() ? -1 : nums2[stack.peek()]);
            stack.push(i);
        }

        for (int i = 0; i < nums1.length; i++) {
            res[i] = map.get(nums1[i]);
        }

        return res;
    }
}