Next Greater Element I Python Solution

lcpy gen -n 496   # by problem number
lcpy gen -s next_greater_element_i   # by problem name

Input: nums1 = [4,1,2], nums2 = [1,3,4,2]
Output: [-1,3,-1]
Explanation: The next greater element for each value of nums1 is as follows:
- 4 is underlined in nums2 = [1,3,4,2]. There is no next greater element, so the answer is -1.
- 1 is underlined in nums2 = [1,3,4,2]. The next greater element is 3.
- 2 is underlined in nums2 = [1,3,4,2]. There is no next greater element, so the answer is -1.

Input: nums1 = [2,4], nums2 = [1,2,3,4]
Output: [3,-1]
Explanation: The next greater element for each value of nums1 is as follows:
- 2 is underlined in nums2 = [1,2,3,4]. The next greater element is 3.
- 4 is underlined in nums2 = [1,2,3,4]. There is no next greater element, so the answer is -1.

class Solution:
    # Time: O(n1 + n2)
    # Space: O(n2)
    def next_greater_element(self, nums1: list[int], nums2: list[int]) -> list[int]:
        next_greater: dict[int, int] = {}
        stack: list[int] = []
        for num in nums2:
            while stack and stack[-1] < num:
                next_greater[stack.pop()] = num
            stack.append(num)
        return [next_greater.get(num, -1) for num in nums1]