class Solution {public:    int maxProfit(vector
     
       &prices) {        if(prices.size() == 0) return 0;        int low = prices[0];        int max = 0;        for(int i =1;i
      
        max) max = prices[i]-low;        }        return max;    }};
      
     

//给定数组，找出最大差值。