Say you have an array for which the ith element is the price of a given stock on day i. If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit. ~~~ public class Solution { public int maxProfit(int[] prices) { if (prices.length<=1) { return 0; } Integer[] mins = new Integer[prices.length]; // first n days Integer[] maxs = new Integer[prices.length]; // last n days mins[0] = prices[0]; maxs[prices.length-1] = prices[prices.length-1]; // fill max prices, from right to left for (int i=prices.length-2; i>=0; i--) { if (prices[i]>maxs[i+1]) maxs[i] = prices[i]; else maxs[i] = maxs[i+1]; } // fill min prices, and calculate the biggest profit, from left to right int biggestProfit = 0; for (int i=1; i<prices.length; i++) { if (prices[i]<mins[i-1]) mins[i] = prices[i]; else mins[i] = mins[i-1]; int profit = maxs[i] - mins[i]; if (profit>biggestProfit) biggestProfit = profit; } return biggestProfit; } } ~~~