49分求助

#include <bits/stdc++.h>
using namespace std;
int main()
{
	int n,t,l,i,max,j;
	vector<int> s;
	cin>>n;
	for(i=1;i<=n;i++)
	{
		cin>>t;
		switch(t)
		{
			case 0:
				cin>>l;
				s.push_back(l);
				break;
			case 1:
				s.pop_back();
				break;
			case 2:
				if(!s.empty())
				{
					max=0;
					for(j=1;j<=s.size();j++)
						if(s.at(j-1)>max)
							max=s.at(j-1);
					cout<<max<<endl;
					break;
				}
				cout<<0;break;
		}
	}
	return 0;
}

AC:#1,#2,#3
TLE:#4,#5
WA:#6