买卖股票的最佳时机 III

Python

class Solution:
    def maxProfit(self, prices):
        if prices==[]:return 0
        length=len(prices)
        b1= [0 for x in prices ]
        s1 = prices[0]
        b1[0]= 0
        for i in range(1,length):
            if s1 < prices[i]:
                b1[i] = max(b1[i-1],prices[i]-s1)
            else:
                b1[i] = b1[i-1]
                s1 = prices[i]
        b2 = [0 for x in prices ]
        s2 =prices[-1]
        b2[-1]=0
        for i in range(-2,-length,-1):
            if s2 >prices [i]:
                b2 [i] = max(b2[i+1],s2-prices[i])
            else:
                b2[i] = b2[i+1]
                s2= prices[i]
        result =0 
        for i in range(length):
            result = max(result , b1[i]+b2[i])
        return result