C++ array sort is giving unexpected results - c++

Question

My code is giving unexpected results. This code is for sorting the elements in the array. Upon running it gives different answer. Can anyone please suggest where the problem might be?
void func(int *arr,int N){
sort(arr,arr+N);
for(int i=0;i<N;i++){
cout<<arr[i]<<" ";}
cout<<endl;
}
int main() {
int N;
int *arr=new int[N];
cin>>N;
for(int j=0;j<N;j++){
cin>>arr[j];
}
func(arr,N);
return 0;
}
Input:
84
1 0 1 2 1 1 0 0 1 2 1 2 1 2 1 0 0 1 1 2 2 0 0 2 2 2 1 1 1 2 0 0 0 2 0 1 1 1 1 0 0 0 2 2 1 2 2 2 0 2 1 1 2 2 0 2 2 1 1 0 0 2 0 2 2 1 0 1 2 0 0 0 0 2 0 2 2 0 2 1 0 0 2 2
Output:
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 0 0 0 0 0 0
0 0 0 1 1 1 1 1 1 1 1 1 1 2 2 2 2 10 807415840 807415840 807415840
807415840 807416096 807416096 807416352 807416352 824193056 824193056
824193312 824193312 824193312 824193568 824193568 824193568 840970272
840970272 840970272 840970272 840970272 840970272 840970272 840970272
840970528 840970528 840970784 840970784 840970784 840970784 840970784

Answer 1

You have an uninitialized variable in your code.
int N;
From the online cpp reference on Uninitialized variables:
It is possible to create a variable without a value. This is very dangerous, but it can give an efficiency boost in certain situations. To create a variable without an initial value, simply don’t include an initial value:
// This creates an uninitialized int
int N;
The value in an uninitialized variable can be anything – it is unpredictable, and may be different every time the program is run. Reading the value of an uninitialized variable is undefined behaviour – which is always a bad idea. It has to be initialized with a value before you can use it.
So before allocating memory of the array based on the value of N, initialize it. In your case, read into it first.
cin>>N;
int *arr=new int[N];
It is also a good practice to check if cin has succeeded and if the value of N is within acceptable bounds before using it.

Answer 2

You are creating the array when N has an indeterminate value, so the result of your program is undefined.
Move this line;
cin>>N;
before this line:
int *arr=new int[N];