给定一个数组,数组中的元素表示股价,第几个元素就代表第几天的股价
设计算法来获得最大的利润,可以进行多次交易(买卖股票多次)
注意:同一时间内不能重复交易(卖股票之后必须先买股票)
Example 1:
Input: [7,1,5,3,6,4] Output: 7 Explanation: Buy on day 2 (price = 1) and sell on day 3 (price = 5), profit = 5-1 = 4. Then buy on day 4 (price = 3) and sell on day 5 (price = 6), profit = 6-3 = 3.
Example 2:
Input: [1,2,3,4,5] Output: 4 Explanation: Buy on day 1 (price = 1) and sell on day 5 (price = 5), profit = 5-1 = 4. Note that you cannot buy on day 1, buy on day 2 and sell them later, as you are engaging multiple transactions at the same time. You must sell before buying again.
Example 3:
Input: [7,6,4,3,1] Output: 0 Explanation: In this case, no transaction is done, i.e. max profit = 0.
1:本题和"买卖股票的最佳时机"类似(https://mp.csdn.net/postedit/82467276),利用头指针pre、尾指针tail和maxProfit即可
def maxProfit(self, prices):
"""
:type prices: List[int]
:rtype: int
"""
if len(prices)<=1:
return 0
pre = prices[0]
tail = prices[0]
maxProfit = 0
for i in prices[1:]:
if i>=tail: #对比当前元素和尾指针的大小
tail=i #替换尾指针为当前元素
else: #累加利润,然后头指针和尾指针从当前元素开始
maxProfit += tail-pre
pre = i
tail = i
maxProfit += tail-pre #累加最后的利润
return maxProfit
算法题来自:https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-ii/description/