Best Time to Buy and Sell Stock with Transaction Fee — C++

// Time:  O(n)
// Space: O(1)

class Solution {
public:
    int maxProfit(vector<int>& prices, int fee) {
        int cash = 0, hold = -prices[0];
        for (int i = 1; i < prices.size(); ++i) {
            cash = max(cash, hold + prices[i] - fee);
            hold = max(hold, cash - prices[i]);
        }
        return cash;
    }
};