714. Best Time to Buy and Sell Stock with Transaction Fee

You are given an array prices where prices[i] is the price of a given stock on the ith day, and an integer fee representing a transaction fee.

Find the maximum profit you can achieve. You may complete as many transactions as you like, but you need to pay the transaction fee for each transaction.

Note: You may not engage in multiple transactions simultaneously (i.e., you must sell the stock before you buy again).

Example 1:
Input: prices = [1,3,2,8,4,9], fee = 2
Output: 8
Explanation: The maximum profit can be achieved by:

• Buying at prices[0] = 1
• Selling at prices[3] = 8
• Buying at prices[4] = 4
• Selling at prices[5] = 9
  The total profit is ((8 - 1) - 2) + ((9 - 4) - 2) = 8.

Example 2:
Input: prices = [1,3,7,5,10,3], fee = 3
Output: 6

Constraints:
1 < prices.length <= 5 104
0 < prices[i], fee < 5 104

Solution:

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8

class Solution:
    def maxProfit(self, prices: List[int], fee: int) -> int:
        dp_hold, dp_not_hold = -float('inf'), 0
        for stock_price in prices:
            dp_not_hold = max(dp_not_hold, dp_hold + stock_price)
            dp_hold = max(dp_hold, dp_not_hold - stock_price - fee)
            
        return dp_not_hold

references

• https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-transaction-fee/