// Source : https://leetcode.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/ // Author : Hao Chen // Date : 2019-02-01 /***************************************************************************************************** * * 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 as many transactions as you like * (ie, buy one and sell one share of the stock multiple times) with the following restrictions: * * You may not engage in multiple transactions at the same time (ie, you must sell the stock * before you buy again). * After you sell your stock, you cannot buy stock on next day. (ie, cooldown 1 day) * * Example: * * Input: [1,2,3,0,2] * Output: 3 * Explanation: transactions = [buy, sell, cooldown, buy, sell] ******************************************************************************************************/ class Solution { public: // //Define // // - buy[i] as the max profit when you buy the stock at day i. // - sell[i] as the max profit when you sell the stock at day i. // // Therefore set buy[0] = -prices[0], because spend the money, the profit is -prices[0]. // Also set sell[0] = 0, that you do nothing in the first day. // // So, // // sell[i] = max ( buy[i-1] + prices[i], // sell[i-1] - prices[i-1] + prices[i] ); // // - buy[i-1]+prices[i] represents buy the stock on day i-1 and sell it on day i; // - sell[i-1]-prices[i-1]+prices[i] represents you didn't sell the stock on day i-1 // but sell it on day i (bought stock back and sell it on day i). // // // buy[i] = max ( sell[i-2] - prices[i], // buy[i-1] + prices[i-1] - prices[i] ); // // - sell[i-2]-prices[i] means sold the stock on day i-2 and buy it on day i // (day i-1 is cooldown). // - buy[i-1]+prices[i-1]-prices[i] means you didn't buy the stock on day i-1 // but buy it on day i. // int maxProfit(vector& prices) { int len = prices.size(); if ( len < 2 ) return 0; vector buy(len, 0); vector sell(len, 0); buy[0] = -prices[0]; int profit = 0; for (int i=1; i