You’re typing a long text with a broken keyboard. Well it’s not so badly broken. The only problem with the keyboard is that sometimes the “home” key or the “end” key gets automatically pressed (internally).
You’re not aware of this issue, since you’re focusing on the text and did not even turn on the monitor! After you finished typing, you can see a text on the screen (if you turn on the monitor).
In Chinese, we can call it Beiju. Your task is to find the Beiju text.
Input
There are several test cases. Each test case is a single line containing at least one and at most 100,000 letters, underscores and two special characters ‘[’ and ‘]’. ‘[’ means the “Home” key is pressed internally, and ‘]’ means the “End” key is pressed internally. The input is terminated by end-of-file (EOF). The size of input file does not exceed 5MB.
Output
For each case, print the Beiju text on the screen.
可以用数组来建立链表，也可以用c++库中的list

#include<cstdio>
#include<cstring>
const int maxn=100005;
int last,cur,next[maxn];//cur表示的是当正要被接的项，last表示最后一个字母的i
char s[maxn];
int main()
{
    while(scanf("%s",s+1) == 1)
    {
        int n=strlen(s+1);
        last=cur=0;
        next[0]=0;
        for(int i=1;i<=n;i++)
        {
            char ch=s[i];
            if(ch == '[') cur = 0;
            else if(ch == ']') cur = last;
            else
            {
                next[i] = next[cur];
                next[cur]=i;
                if(cur==last) last = i;
                cur = i;
            }
        }
        for(int i = next[0];i != 0;i=next[i])
            printf("%c",s[i]);
        printf("\n");
    }
    return 0;
}

#include<cstdio>
#include<list>
#include<iostream>
#include<string>
void solve(std::string s){
    std::list<char> text;
    std::list<char>::iterator it = text.begin();
    for(int i = 0;i < s.length();i++){
        char c = s[i];
        if(c == '['){
            it = text.begin();
        }else if(c == ']'){
            it = text.end();
        }else{
            it = text.insert(it,c);
            it++;//然后指向下一位
        }
    }
    for(it = text.begin();it != text.end();it++){
        std::cout << *it;
    }
    s.clear();//清空好习惯
    std::cout << std::endl;//记得换行
}
int main(){
    std::string s;//读入
    while(std::cin >> s){
        solve(s);
    }
    return 0;
}