[Leetcode] 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) {        if(prices == null || prices.length <= 1) return 0;        int[] left = new int[prices.length];        int[] right = new int[prices.length];        //first DP        int minPrice = prices[0];        left[0] = 0;        for(int i = 1; i < prices.length; i++){            left[i] = Math.max(left[i - 1], prices[i] - minPrice);            minPrice = Math.min(minPrice, prices[i]);        }        //second DP        int maxPrice = prices[prices.length - 1];        right[prices.length - 1] = 0;        for(int i = prices.length - 2; i >= 0; i--){            right[i] = Math.max(right[i + 1], maxPrice - prices[i]);            maxPrice = Math.max(maxPrice, prices[i]);        }        int profit = 0;        for(int i = 0; i < prices.length; i++){            profit = Math.max(profit, left[i] + right[i]);        }        return profit;    }}