StockBuySell.java

import java.util.Arrays;
import java.util.List;

// Uber $ - 5 3 4 6 7 8 9 9  7 6 5 8
// Any day - You can buy 1 stock or you can sell all your stocks or do nothing.
// You have to maximize your profit.
//  (9-5) + (9-3) + (9-4) + (9-6) + (9-7) + (8-7) + (8-6) + (8-5)
//  8, 5, 6, 7, 9, 9, 8
// max = 9
public class StockBuySell {

    public static int maxProfit(List<Integer> list) {
        int max = list.get(list.size()-1);
        int totalProfit = 0;
        for (int i=list.size()-2; i>=0; i--) {
            if (max < list.get(i)) {
                max = list.get(i);
            } else {
                totalProfit = totalProfit + (max - list.get(i));
            }
        }
        return totalProfit;
    }

    public static void main(String[] args) {
        System.out.println(StockBuySell.maxProfit(Arrays.asList(5, 3, 4, 6, 7, 8, 9, 9, 7, 6, 5, 8)));
    }
}