UVa11988 Broken Keyboard (tragic text) !!! stl_list

Title description

The input contains multiple sets of data, and each set of data occupies one line, containing no more than 100,000 letters, underscores, and characters "[" or "]". The character "[" means the Home button and "]" means the End button. Input end flag end of file (EOF) is not more than 5MB input file, for each data output line, i.e. on-screen text tragedy
Sample input:

This_is_a_[Beiju]_text
[[]][]Happy_Birthday_to_Tsinghua_University

Sample output:

BeijuThis_is_a__text
Happy_Birthday_to_Tsinghua_University

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

int main()
{
    while(1){
        int position=100;
        string str;
//    0代表home,100代表end
        cin>>str;
        list<char> de;
        int num=str.length();
        list<char>::iterator t;

        for(int i=0;i<num;i++){
            if(str[i]=='['){
                position=0;
                t=de.begin();
            }
            else if(str[i]==']'){
                position=100;
            }else{
                if(position==0){
                    de.insert(t,str[i]);

                } else{
                    de.push_back(str[i]);
                }
            }
        }
        for(list<char>::iterator it=de.begin();it!=de.end();it++){
            cout<<*it;
        }
        cout<<endl;
    }
    return 0;
}