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转自https://oj.leetcode.com/problems/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).*               **********************************************************************************/class Solution {public:    // Dynamic Programming    //    //     Considering prices[n], and we have a position "i", we could have    //       1) the maxProfit1 for prices[0..i]      //       2) the maxProfit2 for proices[i..n]    //    //    So,     //      for 1) we can go through the prices[n] forwardly.    //          forward[i] = max( forward[i-1], price[i] - lowestPrice[0..i] )     //      for 2) we can go through the prices[n] backwoardly.    //          backward[i] = max( backward[i+1], highestPrice[i..n] - price[i])     //    int maxProfit(vector
   
     &prices) {        if (prices.size()<=1) return 0;        int n = prices.size();        vector
    
      forward(n);        forward[0] = 0;        int lowestBuyInPrice = prices[0];        for(int i=1; i