121. Best Time to Buy and Sell Stock

“”“解题思路：
遍历数组，每次遍历记录数组最小值，并且用计算当前值和最小值之差为利润，记录最大的利润
”“”
class Solution(object):
    def maxProfit(self, prices):
        """
        :type prices: List[int]
        :rtype: int
        """
        if prices == []:
            return 0
        min_num = prices[0]
        max_price = 0
        
        for i in prices[1:]:
            max_price = max(max_price, i-min_num)
            min_num = min(min_num, i)
        
        return max_price