Leetcode 123. Best Time to Buy and Sell Stock III
Say you have an array for which the ith element is the price of a given stock on day i.Design an algorithm to find the maximum profit. You may complete at most two transactions.
Note: You may not engage in multiple transactions at the same time (i.e., you must sell the stock before you buy again).
Example 1:
Input: prices =
Output: 6
Explanation: Buy on day 4 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.
Then buy on day 7 (price = 1) and sell on day 8 (price = 4), profit = 4-1 = 3.
Example 2:
Input: prices =
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: prices =
Output: 0
Explanation: In this case, no transaction is done, i.e. max profit = 0.
Example 4:
Input: prices =
Output: 0
Constraints:
1 <= prices.length <= 10^5
0 <= prices <= 10^5
class Solution:
def maxProfit(self, prices: List) -> int:
if not prices: return 0
hold_first, sold_first = -math.inf, 0
hold_second, sold_second = -math.inf, 0
for price in prices:
hold_first_tmp, sold_first_tmp = hold_first, sold_first
hold_second_tmp, sold_second_tmp = hold_second, sold_second
hold_first = max(hold_first_tmp, 0 - price)
sold_first = max(sold_first_tmp, hold_first_tmp + price)
hold_second = max(hold_second_tmp, sold_first - price)
sold_second = max(sold_second_tmp, hold_second_tmp + price)
return sold_second
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