1 class Solution {
 2     public:
 3         int maxProfit(std::vector<int> &prices)
 4         {
 5             return CaculateProfit(prices, 0, FIRST).profit;
 6         }
 7
 8     private:
 9         struct Profit
10         {
11             Profit() : profit(0), buyPrice(-1), buyDay(0), sellDay(0)
12             {
13             }
14
15             int profit;
16             int buyPrice;
17             int buyDay;
18             int sellDay;
19         };
20
21         enum Transaction
22         {
23             FIRST,
24             SECOND
25         };
26
27         Profit CaculateProfit(std::vector<int> &prices, int start, Transaction transaction )
28         {
29             Profit currentProfit;
30             Profit maxProfit;
31             Profit secondProfit;
32             Profit totalProfit;
33
34             for(int day = start; day < prices.size(); ++day)
35             {
36                 if(currentProfit.buyPrice == -1)
37                 {
38                     currentProfit.buyPrice = prices[day];
39                     currentProfit.buyDay = day;
40                     continue;
41                 }
42
43                 currentProfit.profit = prices[day] - currentProfit.buyPrice;
44                 currentProfit.sellDay = day;
45
46                 if(currentProfit.profit < 0)
47                 {
48                     currentProfit.buyPrice = prices[day];
49                     currentProfit.buyDay = day;
50                     currentProfit.profit = 0;
51                 }
52
53                 if(currentProfit.profit > maxProfit.profit)
54                 {
55                     if(transaction == FIRST)
56                     {
57                         secondProfit = CaculateProfit(prices, day + 1, SECOND);
58
59
60                         if(currentProfit.profit + secondProfit.profit > totalProfit.profit)
61                         {
62                             totalProfit.profit = currentProfit.profit + secondProfit.profit;
63                         }
64                     }
65
66                     maxProfit = currentProfit;
67                 }
68             }
69
70             if(transaction == FIRST)
71             {
72                 return totalProfit;
73             }
74             else
75             {
76                 return maxProfit;
77             }
78         }
79     };