I keep getting zeros when after my original inputs - c++

Question

so im creating a vector with unlimted inputs but i want it so that when the user wants to stop inputing data, they just enter a non numerical key and then just move on to the next vector which is just the first one but reversed and multipled by 8 and 100 added to it but when it should move on, it just adds a bunch of zeros as inputs
#include <iostream>
#include <vector>
using namespace std;
int main() {
int n;
vector<int> (myVec1)(n);
vector<int> (myVec2)(n);
int i;
int sum;
for(i=0;i<n;++i){
cout<<"please enter an integer ";
cin>>myVec1.at(i);
cout<<endl;
if(cin.fail()){
for(i=0; i<n; i++){
cout<<myVec1.at(i)<<" ";
}
}
}
cout<<endl;
for(i=0; i<n; i++){
sum=(myVec1.back()*8)+100;
myVec1.pop_back();
cout<<sum<<" ";
}
return 0;
}
this is the result and as you see theres just a bunch of zeros after i tried to stop the inputs if any one can help me id really appreciate it :)
please enter an integer 435
please enter an integer 412
please enter an integer 43
please enter an integer 56
please enter an integer 2
please enter an integer q
435 412 43 56 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 116 548 444 3396 3580

Answer 1

int n has undefined value (not initialized)
Instead, ignore defining n and initialize your vector like this: vector<int> myVec1;
and when you read values, append them in the vector using myVec1.push_back(valueFromKeyboard);
#include <iostream>
#include <vector>
using namespace std;
int main () {
vector<int> myVec1;
vector<int> myVec2;
int valueFromKeyboard;
cout << "please enter an integer ";
while (cin >> valueFromKeyboard) {
if (!cin.fail()) {
myVec1.push_back(valueFromKeyboard);
}
cout << "please enter an integer ";
}
for (int i = 0; i < myVec1.size(); i++) {
cout << myVec1[i] << " ";
}
cout << endl << endl;
for (int i = 1; i < myVec1.size()+1; i++) {
myVec2.push_back(myVec1.end()[-i]*8+100);
}
for (int i = 0; i < myVec2.size(); i++) {
cout << myVec2[i] << " ";
}
return 0;
}
myVec1.end()[-1] is the last element of the vector, myVec1.end()[-2] is the second to last etc. That's why I created this loop for (int i = 1; i < myVec1.size()+1; i++) to go from 1 to myVec1.size()+1