爬樓梯

class Solution {
public:
     int maxProfit(vector<int> &prices) {
        if(prices.size()==0)
        return 0;
        int min=prices[0],max=0,sum=prices.size();
        for(int i=0;i<sum-1;i++)
        {
            if(prices[i+1]<min)
            {
                min=prices[i+1];
            }
            else
            {
                if(max<prices[i+1]-min)
                max=prices[i+1]-min;
            }
        }
        return max;
    }
};