123. Best Time to Buy and Sell Stock III

Say you have an array for which the ith element is the price of a given stock on day i.
Design an algorithm to find the maximum profit. You may complete at most two transactions.

Note:You may not engage in multiple transactions at the same time (ie, you must sell the stock before you buy again).

public class Solution {
    public int maxProfit(int[] prices) {
        int len = prices.length;
        if(len == 0){
            return 0;
        }
        int f[] = new int[len];
        int b[] = new int[len];
        f[0] = b[len-1] = 0;
        
        int minf = prices[0];        
        int maxb = prices[len-1];
        int ret = 0;
        for(int i=1; i