LeetCode "496. Next Greater Element I" !

Play it in your mind.. or it may be hard to reach to this intuitive solution...

class Solution(object):
    def nextGreaterElement(self, findNums, nums):
        hm = {}
        stk = []
        for n in nums:
            while len(stk)>0 and stk[-1] < n:
                hm[stk[-1]] = n
                stk.pop()
            stk.append(n)

        return list(map(lambda x: hm[x] if x in hm else -1, findNums))