常规题解

#include<iostream>
#include<vector>
using namespace std;

int main() {

int n;
vector<int> a;
cin >> n;
while(n--) {

    char s;
    cin >> s;
    if( s == 'I' ) {

        int x;
        cin >> x;
        a.push_back(x);
        
    }else {

        a.pop_back();
        
    }
    
}

for( int i = 0; i < a.size(); i++ ) {

    cout << a[i] << " ";
    
}

}