How do I get an unlimited length array from the console so that the test starts? What is the end character of the input?

When you use scanf(), generall you can check the return value of scanf(). If the return value is equal to -1, it means that it gets the end of input. Besides, you when you use cin, you can just judge if the input is end by the return value of cin is 0 or not. If it is 0, it means the end.
eg:
int main(){
    int n;
    while(scanf("%d", &n) != -1){
    ....
    }
}

and

int main(){
    int n;
    while(cin >> n){
    ....
    }
}