How to detect a memory leak in c++ program windows/linux when using online IDE?

I am using online IDE to test a memory leak for a simple C++ program like below:

#include <iostream> 
using namespace std; 
int main()
{
int* array = new int[10]; //memory not freed, so should report memory leak
return 0;
}

I am using geeksforgeeks or codechef(gcc 6.3). I read about the memory leak detection, and found 2 ideas like below:

1.

 void* operator new(size_t size, int line)
{
    printf("Allocate %u bytes on line %d\n", size, line);
    return operator new(size);
}

2. something about DEBUG_NEW new (__FILE__, __LINE__)

while debug_new says it only works with MFC. I don't know how to use the 1st option either. Can somebody please help me in pointing out how exactly the memory leak can be discovered in C++ programs on windows/linux?