LeetCode Top Interview 150
188. Best Time to Buy and Sell Stock IV
Hard
You are given an integer array prices where prices[i] is the price of a given stock on the ith day, and an integer k.
Find the maximum profit you can achieve. You may complete at most k transactions.
Note: You may not engage in multiple transactions simultaneously (i.e., you must sell the stock before you buy again).
Example 1:
Input: k = 2, prices = [2,4,1]
Output: 2
Explanation: Buy on day 1 (price = 2) and sell on day 2 (price = 4), profit = 4-2 = 2.
Example 2:
Input: k = 2, prices = [3,2,6,5,0,3]
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.
Constraints:
0 <= k <= 1000 <= prices.length <= 10000 <= prices[i] <= 1000
Solution
from typing import List
class Solution:
def maxProfit(self, k: int, prices: List[int]) -> int:
n = len(prices)
dp = [0] * (k + 1)
maxdp = [float('-inf')] * (k + 1)
for i in range(1, n + 1):
maxdp[0] = max(maxdp[0], dp[0] - prices[i - 1])
for j in range(k, 0, -1):
maxdp[j] = max(maxdp[j], dp[j] - prices[i - 1])
dp[j] = max(maxdp[j - 1] + prices[i - 1], dp[j])
return dp[k]