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

Your are given an array of integers prices, for which the i-th element is the price of a given stock on day i; and a non-negative integer fee representing a transaction fee.

You may complete as many transactions as you like, but you need to pay the transaction fee for each transaction. You may not buy more than 1 share of a stock at a time (ie. you must sell the stock share before you buy again.)

Return the maximum profit you can make.

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.

Note:

0 < prices.length <= 50000.

0 < prices[i] < 50000.

0 <= fee < 50000.

Thought process:
Each day there are two options, buy or sell. Use two variables buy and sell to keep track of the max profit.

Solution:

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class Solution { public int maxProfit(int[] prices, int fee) { if (prices.length == 0) { return 0; } int buy = -prices[0]; int sell = 0; for (int i = 1; i < prices.length; i++) { sell = Math.max(sell, buy + prices[i] - fee); buy = Math.max(buy, sell - prices[i]); } return sell; } }

Time complexity: O(n).