题解

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vector用法：
v.push_back(n);
向v中添加n;
pop_back是删除

#include<bits/stdc++.h>
using namespace std;
int main(){
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    short n;
    cin>>n;
    vector<short> v;
    short x;
    char c;
    for(short i=0;i<n;i++){
        cin>>c;
        if(c=='O'){
            v.pop_back();
        }else{
            cin>>x;
            v.push_back(x);
        }
    }for(short i=0;i<v.size();i++){
        cout<<v[i]<<' ';
    }
    return 0;
}