Question

How to pass reference to a pointer in C++

Answer 1

#include <iostream>

void changeValue(int *p) {
    *p = 700;
}
  
int main()
{
    int n = 12;
    int *p = &n;
  
    std::cout << *p << " " << n << "\n";
  
    changeValue(p);
  
    std::cout << *p << " " << n << "\n";
}
     
     
     
     
/*
run:
   
12 12
700 700
      
*/

 

70+ SQL courses for beginners and professionals

Answer 2

#include <iostream>

int globaln = 33;

void changeValue(int **p) {
    *p = &globaln;
}
  
int main()
{
    int n = 12;
    int *p = &n;
  
    std::cout << *p << " " << n << " " << globaln << "\n";
  
    changeValue(&p);
  
    std::cout << *p << " " << n << " " << globaln << "\n";
}
     
     
     
     
/*
run:
   
12 12 33
33 12 33
      
*/

 

70+ SQL courses for beginners and professionals

Answer 3

#include <iostream>

int globaln = 33;

void changeValue(int *&p) {
    p = &globaln;
}
  
int main()
{
    int n = 12;
    int *p = &n;
  
    std::cout << *p << " " << n << " " << globaln << "\n";
  
    changeValue(p);
  
    std::cout << *p << " " << n << " " << globaln << "\n";
}
     
     
     
     
/*
run:
   
12 12 33
33 12 33
      
*/

 

70+ SQL courses for beginners and professionals