1 #include <vector> 2 #include <iostream> 3 using namespace std; 4  5 class Solution { 6 public: 7     int maxProfit(vector<int> &prices) { 8         //a[i]表示在prices[i]卖出的最大收益（prices[i]-截止a[i]为止的min）。 9         if (prices.size() ==0)10             return 0;11         int min = prices[0];12         int maxP = 0;13         14         for (int i = 1; i < prices.size(); i++)15         {16             if (prices[i] - min>maxP)17                 maxP = prices[i] - min;18             if (prices[i] < min)19                 min = prices[i];20         }21         return maxP;22     }23 };24 int main()25 {26     int a[] = { 5, 2, 4, 9, 7 };27     vector<int> prices(a,a+4);28     Solution s;29     cout << s.maxProfit(prices) << endl;30     return 0;31 }