44分蒟蒻求助，怎么改啊！！！

#include<bits/stdc++.h>
using namespace std;
struct id{
	int s;
	char c;
}a;
int main(){
	deque<id> q;
	string s;
	cin>>s;
	for(int i=0;i<s.length();i++){
		a.c=s[i];
		a.s=i;
		if(!q.empty()){
			if((q.back().c=='(' && s[i]==')')||(q.back().c=='[' && s[i]==']'))
				q.pop_back();
			else
				q.push_back(a);
		}
		else
			q.push_back(a);
	}
	for(int i=0;i<s.length();i++){
		if(!q.empty()){
			if(q.front().s==i){
				if(s[i]=='[')
					cout<<"[]";
				else
					cout<<"()";
				q.pop_front();
			}
			else
				cout<<s[i];
		}
		else
			cout<<s[i];
	}
	return 0;
}