121. Best Time to Buy and Sell Stock

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