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| #include<bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int N = 1000005;
int sum[N] = {};
int f[N] = {};
stack<int> A,B;
int main(){
std::ios::sync_with_stdio(false);
cin.tie(NULL);
char c;
int t;
f[0] = -INF;
sum[0] = 0;
int tmp = 0;
cin >> tmp;
while(tmp--){
cin >> c;
if(c == 'I'){
cin >> t;
A.push(t);
sum[A.size()] = sum[A.size() - 1] + A.top();
f[A.size()] = max(f[A.size() - 1], sum[A.size()]);
}
if(c == 'D'){
if(!A.empty())
A.pop();
}
if(c == 'L'){
if(!A.empty())
{
B.push(A.top());
A.pop();
}
}
if(c == 'R'){
if(!B.empty())
{
A.push(B.top());
B.pop();
sum[A.size()] = sum[A.size() - 1] + A.top();
f[A.size()] = max(f[A.size() - 1], sum[A.size()]);
}
}
if(c == 'Q'){
cin >> t;
cout << f[t] << endl;
}
}
}
|