how to use cin inside for loop?

Question

#include <iostream>
using namespace std;

int main() {

int n,a,b,i,sum,arr [i];
cout << "Please enter amout of number";
cin >> n;

for (i=0;i<n;i++){

cout << "please enter number to sum";
cin >> a; //i try to use cin
//but i can't.
arr[i]=a;
}
while (i<n){
sum+=arr[i];
cout << sum;
}

cout << "sum of number is " << sum;

return 0;
}
https://code.sololearn.com/cW2RN4Wf

Answer 1

now i re write code and has new problem
i can't use the dereference operator *sum and i don't know why. T_T

#include <iostream>
using namespace std;

int main() {

int n,a,b,i,j;
int *sum=nullptr;
sum = new int;
sum = 0;
int *arr =nullptr;
arr = new int[20];

cin >> n;

for (i=0;i<n;i++){

cin >> a; //i try to use cin
//but i can't.
arr[i]=a;
cout << arr[i] << endl ;
}
for (j=0;j<n;j++){
sum+=arr[j];
}

cout << "sum of number is " << sum; //can't use *sum;

return 0;
}

Answer 2

the problen is within arr[i] i assume, not within cin statement.
when you declare an array, you have to give it a static length. for example, make
int arr[n] after the
cin>>n;
this will create an array of int s with the lenght of N. then make a loadup and thell me how it goes

Answer 3

Somebody pls. ans. this becoz I have the same doubt