What causes run time errors in a C++ program?

The basic causes that I have encountered as per my Competitive Coding Experience are :

1. Invalid memory access during run-time.

#include <iostream>
using namespace std;
 
int arr[5];
int main() 
{
 int ans=arr[-1];
 cout<<ans<<endl;
 return 0;
}

2. Accessing linked list nodes that do not exist.

Consider a Linked List :
1->2->3->NULL
 
cout<<head->next->next->next->data<<endl;
// head->next->next->next is actually NULL.

3. Dividing by zero.

#include <iostream>
using namespace std;
 
int main() 
{
 int ans=5/0;
 cout<<ans<<endl;
 return 0;
}

4. Some online judges consider segmentation faults also as run-time errors.

#include <iostream>
using namespace std;
 
int arr[5];

Now suppose in the above example we try to access arr[10] during run-time then a segmentation error occurs which is also treated as run-time errors by many Online Judges for example Leetcode and Interviewbit among others.

5. Large allocation of memory together/Large Static Memory Allocation.

#include <iostream>
using namespace std;
 
int arr[1000000000]; //Note the size of the array.
     //In general around upto 10^8 is usually accepted by all online judges. However to be on the safe side use upto 10^7 unless required.

Try executing the following on your offline compiler (Devcpp for example).

#include <iostream>
using namespace std;
 
int main() {
 int arr[1000000000];
 return 0;
}

6. Making a silly mistake such as this.

#include<bits/stdc++.h>
long long int x;
scanf("%d",&x);

The above code gives run-time error. The reason being x is long long int and scanf should use %lld. I have got a lot of run-time errors for this on online judges such as Codechef.