http://www.phperz.com/article/15/1225/177127.html?from=singlemessage&isappinstalled=0

stock_ops.py

#! encoding=utf8
import unittest


def maxProfit(prices):
    if not prices:
        return 0

    currBuy = -prices[0] #表示当天最终未持股的情况下，当天结束后的累计最大利润
    currSell = 0 #表示当天最终持股的情况下，当天结束后的累计最大利润
    prevSell = 0
    ops = ['buy'] #考虑初始情况
    op_of_today = ''

    for i in xrange(1, len(prices)):
        temp = currSell

        if currBuy + prices[i] > currSell:
            op_of_today = 'sell'
        currSell = max(currSell, currBuy + prices[i])

        if i >= 2:
            if prevSell - prices[i] > currBuy:
                op_of_today = 'buy'
            currBuy = max(currBuy, prevSell - prices[i])
        else:
            if -prices[i] > currBuy:
                op_of_today = 'buy'
            currBuy = max(currBuy, -prices[i])
        prevSell = temp
        ops.append('cooldown' if ops[-1] == 'sell' else op_of_today)

    return currSell, ops


class StockTest(unittest.TestCase):
    def test_something(self):
        self.assertEqual((3, ['buy', 'sell', 'cooldown', 'buy', 'sell']), maxProfit([1, 2, 3, 0, 2]))


if __name__ == '__main__':
    unittest.main()