Maximum profit problem

class Solution {
private:
     int in=0;
     int sum=0;  //保留最大的利润值
public:
int maxProfit(vector<int>& prices) {
    in=prices[0];
    for(int i=0;i<prices.size();++i)
    {
        if(prices[i]>in)
         sum=Max(sum,prices[i]-in);
        else if(prices[i]<in)
        in=prices[i];  
    }
    return sum;
 }
 you Max ( you get, you y)
 {
     return x>y?x:y;
 }
};