Leetcode121. Best Time to Buy and Sell Stock

class Solution:
    def maxProfit(self, prices: List[int]) -> int:
        if prices==None or len(prices)<2:
            return 0
        dp = list(range(len(prices)))
        dp[0]=0
        minValue = prices[0]
        ans = 0
        for i in range(1,len(prices)):
            dp[i]=prices[i]-minValue
            minValue = prices[i] if prices[i]<minValue else minValue
            ans = dp[i] if dp[i]>ans else ans
        return ans

Runtime: 44 ms, faster than 84.53% of Python3 online submissions for Best Time to Buy and Sell Stock.
Memory Usage: 14.8 MB, less than 5.08% of Python3 online submissions for Best Time to Buy and Sell Stock.