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

Problem

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).

• The transaction fee is only charged once for each stock purchase and sale.

  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

• 1 <= prices[i] < 5 * 104

• 0 <= fee < 5 * 104

Solution

/**
 * @param {number[]} prices
 * @param {number} fee
 * @return {number}
 */
var maxProfit = function(prices, fee) {
    var hasStock = Number.MIN_SAFE_INTEGER;
    var hasNoStock = 0;
    for (var i = 0; i < prices.length; i++) {
        var a = Math.max(hasStock, hasNoStock - prices[i]);
        var b = Math.max(hasNoStock, hasStock + prices[i] - fee);
        hasStock = a;
        hasNoStock = b;
    }
    return Math.max(hasStock, hasNoStock);
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).