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;
}
}