How to release the memory allocated by a pointer in C++?

What does the following C++ code do?

#include<iostream>
using namespace std;
int main() {
    int *ptr = NULL;
    ptr = new int;
    *ptr = 7;
    cout << *ptr;
    delete ptr;
    return 0;
}

How do you dynamically allocate memory for an array in C++ using pointers?

What is the correct way to dynamically create an object in C++?

typedef struct Student
{
 int rollno;
 int total;
} Student;
Student s1;
struct Student s2;

Which statement is correct?

Consider the following three C functions:

[PI] int * g (void) 
{ 
  int x= 10; 
  return (&x); 
}  
  
[P2] int * g (void) 
{ 
  int * px; 
  *px= 10; 
  return px; 
} 
  
[P3] int *g (void) 
{ 
  int *px; 
  px = (int *) malloc (sizeof(int)); 
  *px= 10; 
  return px; 
}

Which of the above functions are likely to cause problems with pointers?

Consider the following program. Where are i, j and *k stored in memory?

int i;
int main()
{
    int j;
    int *k = (int *) malloc (sizeof(int));
}

int main() {
    char p[]="geeksquiz";
    char t;
    int i,j;
    for(i=0,j=strlen(p);i!=j;i++,j--)
    {
        t=p[i];
        p[i]=p[j-i];
        p[j-i]=t;
    }
    printf("%s",p);
    return 0;
}

Output?

The most appropriate matching for the following pairs (GATE CS 2000)

What is returned by malloc() if the allocation fail?