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 k transactions.
Note:
You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).
Example 1:
Input: [2,4,1], k = 2
Output: 2
Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2.
Example 2:
Input: [3,2,6,5,0,3], k = 2
Output: 7
Explanation: Buy on day 2 (price = 2) and sell on day 3 (price = 6), profit = 6-2 = 4.
Then buy on day 5 (price = 0) and sell on day 6 (price = 3), profit = 3-0 = 3.
My code:
class Solution(object):
def maxProfit(self, k, prices):
"""
:type k: int
:type prices: List[int]
:rtype: int
"""
if (len(prices) == 0) or k == 0:
return 0
if k >= len(prices) / 2:
return sum(i - j for i, j in zip(prices[1:], prices[:-1]) if i - j > 0)
#k is smaller than len/2 now
b = [-float('inf')]*(k+1)#local best i days with j transactions
s = [0] * (k+1)#global best i days with j transactions
for i in range(1,len (prices)+1):
for j in range(1,min(i+1,k+1)):
b[j],s[j] = max(b[j],s[j-1]-prices[i-1]),max(s[j],b[j] + prices[i-1])
return max(s)Solution: https://leetcode.com/problems/best-time-to-buy-and-sell-stock-iv/