无法指出发生分段错误的位置

Question

I am supposed to print the largest element of the stack (using vector to implement stack here) whenever i encounter a query "Q" it works just fine when i run it against some sample testcases but whenever i submit the code it gives me segmentation fault.

when the query is A 10 Add 10 to stack , when query is R pop element from stack , when query is Q print the largest element in the stack

#include <stdio.h>
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
using namespace std;


int main() {
   int t=0;
    cin>>t;

    for(int x=0;x<t;x++){
      printf("Case %d:\n",x+1);  
     int q=0;
        cin>>q;
        vector<int> myvec;
        vector<int> trackvec;
        int top=-1;

        for(int i=0;i<q;i++){
            string s;
            cin>>s;
            if(s=="A"){
              int num=0;
                cin>>num;
                myvec.push_back(num);
                if(i==0){trackvec.push_back(num);top++;}
                else{
                    if(num>trackvec[top]){
                     trackvec.push_back(num);   
                        top++;
                    }                   
                    else{
                        trackvec.push_back(trackvec[top]);
                        top++;
                    }
                }

            }

            else if(s=="R"){
                myvec.pop_back();
                trackvec.pop_back();
                top--;
            }
            else if(s=="Q" && top==-1){
                cout<<"Empty"<<endl;
            }
            else if(s=="Q"){
                cout<<trackvec[top]<<endl;
            }


    }
}
}
The trackvec here is to keep track of the largest element 

Sample input:
2
7
A 10
A 5
Q
A 100
Q
R
Q
6
A 5
Q
R
Q
R
R

Answer 1

I have edited the post you can check the sample inputs, but the code does work well for those sample inputs

Your first task should be to produce an input that causes the crash. What assumptions are you making with respect to how many A s and R s there are in the input?

Here is an input that produces segmentation fault on my system:

1
2
R
Q

The fix is hopefully obvious to you now.