I check some tests where I get from forum, but my program got WA9.

it is my code :

#include <iostream>
#include <cstdio>
#include <string>
#include <vector>

#define For(i , n) for (int i = 0; i < n; i++)
#define FOR(i , n) for (int i = n - 1; i >= 0; i--)

using namespace std;

struct Char
{
  char ch;
  int used;
  Char(char c,int u) { ch = c; used = u; }
};

string seq;
vector<Char> stck;

void insert(int i)
{
   if (stck[i].ch == '(') stck.insert(stck.begin() + i + 1, Char(')', 1));
   else if (stck[i].ch == ')')
    {
     stck.erase(stck.begin() + i);
     stck.insert(stck.begin() + i , Char('(' , 1));
     stck.insert(stck.begin() + i + 1 , Char(')' , 1));
    }
   else if (stck[i].ch == '[') stck.insert(stck.begin() + i + 1, Char(']', 1));
   else if (stck[i].ch == ']')
    {
     stck.erase(stck.begin() + i);
     stck.insert(stck.begin() + i , Char('[' , 1));
     stck.insert(stck.begin() + i + 1 , Char(']' , 1));
    }
}

void search(char ch,int from)
{
  int res = 0 , pos = from;
  bool ok = true;
  FOR(i , from)
   if (stck[i].ch == ch && !stck[i].used) {
      stck[i].used = 1;
      pos = i,
      ok = false;
      break;
    }
  for (int i = from - 1; i > pos; i--)
   if (!stck[i].used)
    {
     stck[i].used = 1; ok = false;
     insert(i);
    }
   if (ok) stck[from - 1].used = 1 , insert(from - 1);
}

int main()
{
 cin>>seq;
 stck.clear();
 For(i , seq.length())
  {
    stck.push_back(Char(seq[i],0));
    if (stck.back().ch == ')') stck.back().used = 1 , search('(' , stck.size());
    else if (stck.back().ch == ']') stck.back().used = 1 , search('[' , stck.size());
  }
 For(i , stck.size())
  {
   if (!stck[i].used)
    {
     stck[i].used = 1;
     insert(i);
    }
  }
 For(i , stck.size())
  cout<<stck[i].ch;
 cout<<endl;

 return 0;
}

sorry for my english.