Final Prices With a Special Discount in a Shop — Python

# Time:  O(n)
# Space: O(n)

class Solution(object):
    def finalPrices(self, prices):
        """
        :type prices: List[int]
        :rtype: List[int]
        """
        stk = []
        for i, p in enumerate(prices):
            while stk and prices[stk[-1]] >= p:
                prices[stk.pop()] -= p
            stk.append(i)
        return prices