Leetcode 123. Best Time to Buy and Sell Stock III (Hard) (cpp)

Leetcode 123. Best Time to Buy and Sell Stock III (Hard) (cpp)

Tag: Array, Dynamic Programming

Difficulty: Hard

/*

123. Best Time to Buy and Sell Stock III (Hard)

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).

*/
class Solution {
public:
	int maxProfit(vector<int>& prices) {
		if (prices.size() < 2) {
			return 0;
		}
		vector<int> pro(prices.size());
		pro[0] = 0;
		int buy = prices[0];
		for (int i = 1; i < prices.size(); i++) {
			pro[i] = max(pro[i - 1], prices[i] - buy);
			buy = min(buy, prices[i]);
		}
		int sell = prices.back(), best = 0;
		for (int i = prices.size() - 2; i >= 0; i--) {
			best = max(best, sell - prices[i] + pro[i]);
			sell = max(sell, prices[i]);
		}
		return best;
	}
};