Unaccepted求调

#include<bits/stdc++.h>
using namespace std;
struct character{
    char c;
    int id;
};
int main()
{
    string str;
    getline(cin,str);
    vector <bool> s(str.size(),false);
    stack<character> p;
    for(int i=0;i<str.size();i++)
    {
        char ch=str[i];
        if(ch=='('||ch=='[')
            p.push({ch,i});
        else{
            if(!p.empty()){
                character q=p.top();
                if((q.c=='('&&ch==')')||(q.c=='['&&ch==']')){
                    s[i]=true;
                    s[q.id]=true;
                    p.pop();
                }else{
                    p.pop();
                }
            }
        }
    }
    string ans="";
    for(int i=0;i<str.length();i++)
    {
        if(!s[i]){
            if(str[i]=='('||str[i]==')')
                ans+="()";
            else
                ans+="[]";
        }else{
            ans+=str[i];
        }
    }
    cout<<ans<<endl;
    return 0;
}