爬樓梯

class Solution {
public:
    int maxProfit(vector<int> &prices) {
        // write your code here
  /* if(prices.size()==0){
       return 0;
   }*/
          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;
    }
};